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19-0467; Rev 2; 5/97
NUAL KIT MA UATION BLE EVAL AVAILA
300MHz High-Speed Op Amp
____________________________Features
o High Speed: 300MHz -3dB Bandwidth (AV = +1) 200MHz Full-Power Bandwidth (AV = +1, Vo = 2Vp-p) 1100V/s Slew Rate 130MHz 0.1dB Gain Flatness o Drives 100pF Capacitive Loads Without Oscillation o Low Differential Phase/Gain Error: 0.01/0.01% o 8mA Quiescent Current o Low Input-Referred Voltage Noise: 5nV/Hz o Low Input-Referred Current Noise: 2pA/Hz o Low Input Offset Voltage: 0.5mV o 8000V ESD Protection o Voltage-Feedback Topology for Simple Design Configurations o Short-Circuit Protected o Available in Space-Saving SOT23 Package
_______________General Description
The MAX477 is a 5V wide-bandwidth, fast-settling, unity-gain-stable op amp featuring low noise, low differential gain and phase errors, high slew rate, high precision, and high output current. The MAX477's architecture uses a standard voltage-feedback topology that can be configured into any desired gain setting, as with other general-purpose op amps. Unlike high-speed amplifiers using current-mode feedback architectures, the MAX477 has a unique input stage that combines the benefits of the voltage-feedback design (flexibility in choice of feedback resistor, two high-impedance inputs) with those of the currentfeedback design (high slew rate and full-power bandwidth). It also has the precision of voltage-feedback amplifiers, characterized by low input-offset voltage and bias current, low noise, and high common-mode and power-supply rejection. The MAX477 is ideally suited for driving 50 or 75 loads. Available in DIP, SO, space-saving MAX, and SOT23 packages.
MAX477
________________________Applications
Broadcast and High-Definition TV Systems Video Switching and Routing Communications Medical Imaging Precision DAC/ADC Buffer
______________Ordering Information
PART MAX477EPA MAX477ESA MAX477EUA MAX477EUK-T MAX477MJA TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -55C to +125C PINPACKAGE 8 Plastic DIP 8 SO 8 MAX 5 SOT23 8 CERDIP SOT TOP MARK -- -- -- ABYW --
__________Typical Operating Circuit
__________________Pin Configuration
TOP VIEW
VIN 75 75 VOUT OUT 1 75 500 500 VEE 2
MAX477
5 VCC N.C. 1 IN- 2 IN+ 3 4 INVEE 4
MAX477
8 7 6 5 N.C. VCC OUT N.C.
MAX477
IN+ 3 VIDEO/RF CABLE DRIVER
SOT23-5
DIP/SO/MAX
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.
300MHz High-Speed Op Amp MAX477
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC to VEE) ..................................................12V Differential Input Voltage..................(VCC + 0.3V) to (VEE - 0.3V) Common-Mode Input Voltage..........(VCC + 0.3V) to (VEE - 0.3V) Output Short-Circuit Duration to GND........................Continuous Continuous Power Dissipation (TA = +70C) Plastic DIP (derate 9.09mW/C above +70C)..............727mW SO (derate 5.88mW/C above +70C) ..........................471mW MAX (derate 4.1mW/C above +70C) .......................330mW CERDIP (derate 8.00mW/C above +70C) ..................640mW SOT23 (derate 7.1mW/C above +70C) ......................571mW Operating Temperature Ranges MAX477E_A ......................................................-40C to +85C MAX477EUK .....................................................-40C to +85C MAX477MJA ...................................................-55C to +125C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, VOUT = 0V, RL = , TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL MAX477EUK MAX477ESA/EPA/EUA/MJA MAX477EUK Input Offset-Voltage Drift Input Bias Current Input Offset Current Differential-Mode Input Resistance Common-Mode Input Voltage Range Common-Mode Rejection Ratio Power-Supply Rejection Ratio Open-Loop Voltage Gain Open-Loop Voltage Gain TCVOS IB IOS RIN(DM) VCM CMRR PSRR AVOL TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX Either input TA = +25C TA = TMIN to TMAX TA = +25C TA = TMIN to TMAX VS = 4.5V to 5.5V VOUT = 2.0V, VCM = 0V, RL = 50 TA = +25C Output Voltage Swing Minimum Output Current Short-Circuit Output Current Open-Loop Output Resistance Quiescent Supply Current VOUT IOUT ISC ROUT ISY TA = TMIN to TMAX TA = -40 C to +85 C Short to ground VOUT = 0, f = DC TA = +25C MAX477E_ _, TA = TMIN to TMAX MAX477MJA, TA = TMIN to TMAX MAX477E_A/477MJA MAX477EUK RL = RL = 100 RL = 50 VCM = 3V VCM = 2.5V 3.0 2.5 70 60 70 55 50 3.5 3.0 2.5 70 100 150 0.1 8 10 12 14 mA mA mA mA 85 65 65 3.9 V 90 1 3.5 0.2 CONDITIONS MAX477ESA/EPA/EUA/MJA Input Offset Voltage VOS TA = +25C TA = TMIN to TMAX 2 1 3 5.0 1.0 2.0 MIN TYP 0.5 0.5 MAX 2.0 2.0 3.0 5.0 V/C A A M V dB dB dB mV UNITS
2
_______________________________________________________________________________________
300MHz High-Speed Op Amp
AC ELECTRICAL CHARACTERISTICS
(VCC = +5V, VEE = -5V, RL = 100, AVCL = +1, TA = +25C, unless otherwise noted.) PARAMETER Small-Signal, -3dB Bandwidth (Note 2) Small-Signal, 0.1dB Gain Flatness (Note 2) Full-Power Bandwidth Slew Rate (Note 2) Settling Time Rise Time, Fall Time Input Voltage Noise Density Input Current Noise Density Differential Gain (Note 3) Differential Phase (Note 3) Differential-Mode Input Capacitance Output Impedance Total Harmonic Distortion Spurious-Free Dynamic Range Third-Order Intercept SYMBOL BW-3dB BW0.1dB FPBW SR tS tR, tF en in DG DP CIN(DM) ZOUT THD SFDR IP3 VOUT 0.1Vp-p VOUT 0.1Vp-p VOUT = 2Vp-p VOUT = 2Vp-p VOUT = 2V Step VOUT = 2V Step f = 10MHz f = 10MHz, either input f = 3.58MHz f = 3.58MHz Either input f = 10MHz fc = 10MHz, VOUT = 2Vp-p f = 5MHz, VOUT = 2Vp-p f = 10MHz, VOUT = 2Vp-p to 0.1% to 0.01% 700 CONDITIONS MIN 220 30 TYP 300 130 200 1100 10 12 2 5 2 0.01 0.01 1 2.5 -58 -74 36 MAX UNITS MHz MHz MHz V/s ns ns nV/Hz pA/Hz % degrees pF dB dBc dBm
MAX477
Note 1: Specifications for the MAX477EUK (SOT23 package) are 100% tested at TA = +25C, and guaranteed by design over temperature. Note 2: Maximum AC specifications are guaranteed by sample test on the MAX477ESA only. Note 3: Tested with a 3.58MHz video test signal with an amplitude of 40IRE superimposed on a linear ramp (0 to 100IRE). An IRE is a unit of video-signal amplitude developed by the Institute of Radio Engineers. 140IRE = 1V.
__________________________________________Typical Operating Characteristics
(VCC = +5V, VEE = -5V, RL = 100, CL = 0pF, TA = +25C, unless otherwise noted.)
SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +1V/V)
MAX477-01
SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +2V/V)
MAX477-02
SMALL-SIGNAL GAIN vs. FREQUENCY (AVCL = +10V/V)
21 20 19 GAIN (dB) 18 17 16 15 14 13 12
MAX477-03
2 1 0 -1 GAIN (dB)
8 7 6 5 GAIN (dB) 4 3 2 1 0 -1 -2
22
-2 -3 -4 -5 -6 -7 -8 1M 10M 100M 1G FREQUENCY (Hz)
1M
10M
100M
1G
100k
1M
10M
100M
FREQUENCY (Hz)
FREQUENCY (Hz)
_______________________________________________________________________________________
3
300MHz High-Speed Op Amp MAX477
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, CL = 0pF, TA = +25C, unless otherwise noted.)
GAIN FLATNESS vs. FREQUENCY (AVCL = +1V/V)
MAX477-04
LARGE-SIGNAL GAIN vs. FREQUENCY (AVCL = +1V/V)
2 1 0 GAIN (dB) -1 -2 -3 -4 -5 -6 VOLTAGE (100mV/div) OUT
MAX477-05
SMALL-SIGNAL PULSE RESPONSE (AVCL = +1V/V)
0.2 0.1 0 GAIN (dB) -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 1M 10M 100M
3
IN
GND
GND
1G
1M
10M
100M
1G
TIME (10ns/div)
FREQUENCY (Hz)
FREQUENCY (Hz)
SMALL-SIGNAL PULSE RESPONSE (AVCL = +2V/V)
SMALL-SIGNAL PULSE RESPONSE (AVCL = +10V/V)
LARGE-SIGNAL PULSE RESPONSE (AVCL = +1V/V)
IN (50mV/ div) VOLTAGE OUT (100mV/ div)
GND
IN (50mV/ div) VOLTAGE
GND
IN VOLTAGE (2V/div)
GND
GND
OUT (500mV/ div)
GND
OUT
GND
TIME (10ns/div)
TIME (50ns/div)
TIME (10ns/div)
LARGE-SIGNAL PULSE RESPONSE (AVCL = +2V/V)
LARGE-SIGNAL PULSE RESPONSE (AVCL = +10V/V)
SMALL-SIGNAL PULSE RESPONSE (AVCL = +1V/V, CL = 50pF)
IN (1V/div) VOLTAGE
GND
IN (200mV/ div) VOLTAGE
GND IN VOLTAGE (100mV/div) GND OUT
GND
OUT (2V/div)
GND
OUT (2V/div)
GND
TIME (10ns/div)
TIME (50ns/div)
TIME (20ns/div)
4
_______________________________________________________________________________________
300MHz High-Speed Op Amp
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, CL = 0pF, TA = +25C, unless otherwise noted.)
MAX477
SMALL-SIGNAL PULSE RESPONSE (AVCL = +1V/V, CL = 100pF)
LARGE-SIGNAL PULSE RESPONSE (AVCL = +1V/V, CL = 50pF)
LARGE-SIGNAL PULSE RESPONSE (AVCL = +1V/V, CL = 100pF)
GND IN VOLTAGE (100mV/div) OUT GND
IN VOLTAGE (2V/div) OUT
GND IN VOLTAGE (2V/div) GND OUT
GND
GND
TIME (20ns/div)
TIME (20ns/div)
TIME (20ns/div)
INPUT OFFSET VOLTAGE (VOS) vs. TEMPERATURE
MAX477-17
QUIESCENT SUPPLY CURRENT (ISY) vs. TEMPERATURE
MAX477-18
INPUT BIAS CURRENT (IB) vs. TEMPERATURE
VCM = 0V
MAX477-19
400 INPUT OFFSET VOLTAGE (V) 300 200 100 0 -100 -200 -300 -50 -25 0 25 50 75 100 VCM = 0V
14 QUIESCENT SUPPLY CURRENT (mA) 12 10 8 6 4 2 0
3.5 3.0 INPUT BIAS CURRENT (A) 2.5 2.0 1.5 1.0 0.5 0 -50
125
-50
-25
0
25
50
75
100
125
-25
0
25
50
75
100
125
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
OUTPUT VOLTAGE SWING vs. TEMPERATURE
MAX477-20
INPUT COMMON-MODE RANGE (VCM) vs. TEMPERATURE
MAX477-21
4.2 4.0 COMMON-MODE RANGE (V) 3.8 3.6 3.4 3.2 3.0
OUTPUT VOLTAGE SWING (V)
4.0
RL =
8
3.5
RL = 100 RL = 50
3.0
2.5 -50
2.8 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) TEMPERATURE (C)
_______________________________________________________________________________________
5
300MHz High-Speed Op Amp MAX477
____________________________Typical Operating Characteristics (continued)
(VCC = +5V, VEE = -5V, RL = 100, CL = 0pF, TA = +25C, unless otherwise noted.)
POWER-SUPPLY REJECTION vs. FREQUENCY
MAX477-22
OUTPUT IMPEDANCE vs. FREQUENCY
MAX477-23
-20 POWER SUPPLY REJECTJION (dB) -30 -40 -50 -60 -70 -80 -90 -100 -110 30k 100k 1M FREQUENCY (Hz) 10M
1k
OUTPUT IMPEDANCE () 100M
100
10
1
0.1 100k 1M 10M 100M 500M FREQUENCY (Hz)
HARMONIC DISTORTION vs. FREQUENCY
MAX477-24
OPEN-LOOP GAIN AND PHASE vs. FREQUENCY
10 8 6 OPEN-LOOP GAIN (dB)
MAX477-16
-20
360
-40 DISTORTION (dB)
2 0 -2 -4 -6 -8 -360 100M FREQUENCY (Hz) 500M PHASE 0
-60
TOTAL HARMONIC DISTORTION SECOND HARMONIC THIRD HARMONIC
-180
-80
-100 1k 10k 100k 1M 10M 100M FREQUENCY (Hz)
-10 50M
DIFFERENTIAL GAIN AND PHASE (AVCL = +1, RL = 150)
MAX477-25
DIFFERENTIAL GAIN AND PHASE (AVCL = +2, RL = 150)
DIFF GAIN (%) 0.000 -0.004 -0.008 -0.012 0 IRE DIFF PHASE (deg) 0.003 0.002 0.001 0.000 -0.001 -0.002 0 IRE 100 100
MAX477-26
DIFF GAIN (%)
0.006 0.004 0.002 0.000 -0.002 -0.004 0 IRE
0.004
100
DIFF PHASE (deg)
0.006 0.004 0.002 0.000 -0.002 -0.004 0 IRE 100
6
_______________________________________________________________________________________
PHASE (DEGREES)
4
GAIN
180
300MHz High-Speed Op Amp
_____________________Pin Description
PIN SO/MAX/DIP 1, 5, 8 2 3 4 6 7 SOT23 -- 4 3 2 1 5 NAME N.C. ININ+ VEE OUT VCC FUNCTION No Connect. Not internally connected. Inverting Input Noninverting Input Negative Power Supply Amplifier Output Positive Power Supply
Output Short-Circuit Protection
Under short-circuit conditions, the output current is typically limited to 150mA. This is low enough that a short to ground of any duration will not cause permanent damage to the chip. However, a short to either supply will significantly increase the power dissipation and may cause permanent damage. The high outputcurrent capability is an advantage in systems that transmit a signal to several loads. See High-Performance Video Distribution Amplifier in the Applications Information section.
MAX477
__________Applications Information
Grounding, Bypassing, and PC Board Layout
To obtain the MAX477's full 300MHz bandwidth, Microstrip and Stripline techniques are recommended in most cases. To ensure the PC board does not degrade the amplifier's performance, design the board for a frequency greater than 1GHz. Even with very short traces, use these techniques at critical points, such as inputs and outputs. Whether you use a constant-impedance board or not, observe the following guidelines when designing the board: * Do not use wire-wrap boards. They are too inductive. * Do not use IC sockets. They increase parasitic capacitance and inductance. * In general, surface-mount components have shorter leads and lower parasitic reactance, giving better high-frequency performance than through-hole components. * The PC board should have at least two layers, with one side a signal layer and the other a ground plane. * Keep signal lines as short and straight as possible. Do not make 90 turns; round all corners. * The ground plane should be as free from voids as possible.
_______________Detailed Description
The MAX477 allows the flexibility and ease of a classic voltage-feedback architecture while maintaining the high-speed benefits of current-mode feedback (CMF) amplifiers. Although the MAX477 is a voltage-feedback op amp, its internal architecture provides an 1100V/s slew rate and a low 8mA supply current. CMF amplifiers offer high slew rates while maintaining low supply current, but use the feedback and load resistors as part of the amplifier's frequency compensation network. In addition, they have only one input with high impedance. The MAX477 has speed and power specifications like those of current-feedback amplifiers, but has high input impedance at both input terminals. Like other voltagefeedback op amps, its frequency compensation is independent of the feedback and load resistors, and it exhibits a constant gain-bandwidth product. However, unlike standard voltage-feedback amplifiers, its largesignal slew rate is not limited by an internal current source, so the MAX477 exhibits a very high full-power bandwidth.
RG VIN
RF
RG
RF
MAX477
VOUT VIN
MAX477
VOUT
VOUT = -(RF/RG) VIN
VOUT = [1 + (RF/RG)] VIN
Figure 1a. Inverting Gain Configuration
Figure 1b. Noninverting Gain Configuration
7
_______________________________________________________________________________________
300MHz High-Speed Op Amp MAX477
RG VIN RF
Table 1. Resistor and Bandwidth Values for Various Closed-Loop Gain Configurations
GAIN (V/V) Rg () Open 500 125 50 300 150 100 50 Rf () Short 500 500 450 300 300 500 500 -3dB BANDWIDTH (MHz) 300 120 25 12 114 64 42 23
C
MAX477
RL
VOUT
+1 +2 +5 +10 -1 -2 -5 -10
Figure 2. Effect of High-Feedback Resistor Values and Parasitic Capacitance on Bandwidth
Setting Gain
The MAX477 can be configured as an inverting or noninverting gain block in the same manner as any other voltage-feedback op amp. The gain is determined by the ratio of two resistors and does not affect amplifier frequency compensation. This is unlike CMF op amps, which have a limited range of feedback resistors, typically one resistor value for each gain and load setting. This is because the -3dB bandwidth of a CMF op amp is set by the feedback and load resistors. Figure 1a shows the inverting gain configuration and its gain equation, while Figure 1b shows the noninverting gain configuration.
that the MAX477's voltage-feedback architecture provides a precision amplifier with significantly lower DC errors and lower noise compared to CMF amplifiers. 1) In Figure 3, total output offset error is given by: R VOUT = 1+ f Rg V + I R - I R || R + I g OS RS + R f || Rg OS B S B f
(
)
((
))
Choosing Resistor Values The feedback and input resistor values are not critical in the inverting or noninverting gain configurations (as with current-feedback amplifiers). However, be sure to select resistors that are small and noninductive. Surface-mount resistors are best for high-frequency circuits. Their material is similar to that of metal-film resistors, but to minimize inductance, it is deposited in a flat, linear manner using a thick film. Their small size and lack of leads also minimize parasitic inductance and capacitance. The MAX477's input capacitance is approximately 1pF. In either the inverting or noninverting configuration, excess phase resulting from the pole frequency formed by Rf || Rg and C can degrade amplifier phase margin and cause oscillations (Figure 2). Table 1 shows the recommended resistor combinations and measured bandwidth for several gain values.
For the special case in which RS is arranged to be equal to Rf || Rg, the IB terms cancel out. Note also, for IOS (RS + (Rf || Rg) << VOS, the IOS term also drops out of the equation for total DC error. In practice, high-speed configurations for the MAX477 necessitate the use of low-value resistors for RS, Rf, and Rg. In this case, the VOS term is the dominant DC error source. 2) The MAX477's total input-referred noise in a closedloop feedback configuration can be calculated by: eT = where en
2 2 2 en + eR + inREQ
(
)
DC and Noise Errors
The standard voltage-feedback topology of the MAX477 allows DC error and noise calculations to be done in the usual way. The following analysis shows
8
= input-referred noise voltage of the MAX477 (5nVHz) in = input-referred noise current of the MAX477 (2pAHz) REQ = total equivalent source resistance at the two inputs, i.e., REQ = RS + Rf || Rg eR = resistor noise voltage due to REQ, i.e., eR = 4KT REQ
_______________________________________________________________________________________
300MHz High-Speed Op Amp MAX477
As an example, consider RS = 75, Rf = Rg = 500. Then: REQ = 75 + 500 || 500 = 325 eR eT = 4KT x 325 = 2.3nV / Hz at 25C =
IBRS VIN VOUT Rg Rf
(
)
(
5nV
)(
2
+ 2.3nV
)(
2
+ 2pA x 325
)
2
= 5.5nV Hz
IB+
MAX477
3) The MAX477's output-referred noise is simply total input-referred noise, e T , multiplied by the gain factor: R eOUT = e T 1+ f Rg In the above example, with eT = 5.5nVHz, and assuming a signal bandwidth of 300MHz (471MHz noise bandwidth), total output noise in this bandwidth is: 500 eOUT = 5.5nV x 1 + x 500
Figure 3. Output Offset Voltage
15 10 5 GAIN (dB) 0 -5 -10 -15 -20 1M 10M 100M 1G FREQUENCY (Hz) CL = 0pF CL = 100pF CL = 41pF CL = 22pF
471MHz = 239VRMS
Note that for both DC and noise calculations, errors are dominated by offset voltage (VOS) and input noise voltage (en). For a current-mode feedback amplifier with offset and noise errors significantly higher, the calculations are very different.
Driving Capacitive Loads
The MAX477 provides maximum AC performance with no output load capacitance. This is the case when the MAX477 is driving a correctly terminated transmission line (i.e., a back-terminated 75 cable). However, the MAX477 is capable of driving capacitive loads up to 100pF without oscillations, but with reduced AC performance. Driving large capacitive loads increases the chance of oscillations in most amplifier circuits. This is especially true for circuits with high loop gain, such as voltage followers. The amplifier's output resistance and the load capacitor combine to add a pole and excess phase to the loop response. If the frequency of this pole is low enough and phase margin is degraded sufficiently, oscillations may occur. A second problem when driving capacitive loads results from the amplifier's output impedance, which looks inductive at high frequency. This inductance forms an L-C resonant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier's gain margin.
Figure 4. Effect of CLOAD on Frequency Response (AVCL = +1V/V)
The MAX477 drives capacitive loads up to 100pF without oscillation. However, some peaking (in the frequency domain) or ringing (in the time domain) may occur. This is shown in Figure 4 and the in the Small and Large-Signal Pulse Response graphs in the Typical Operating Characteristics. To drive larger-capacitance loads or to reduce ringing, add an isolation resistor between the amplifier's output and the load, as shown in Figure 5. The value of RISO depends on the circuit's gain and the capacitive load. Figure 6 shows the Bode plots that result when a 20 isolation resistor is used with a voltage follower driving a range of capacitive loads. At the higher capacitor values, the bandwidth is dominated by the RC network, formed by RISO and CL; the bandwidth of the amplifier itself is much higher. Note that adding an isolation resistor degrades gain accuracy. The load and isolation resistor form a divider that decreases the voltage delivered to the load.
9
_______________________________________________________________________________________
300MHz High-Speed Op Amp MAX477
Flash ADC Preamp
The MAX477's high output-drive capability and ability to drive capacitive loads make it well suited for buffering the low-impedance input of a high-speed flash ADC. With its low output impedance, the MAX477 can drive the inputs of the ADC while maintaining accuracy. Figure 7 shows a preamp for digitizing video, using the 250Msps MAX100 and the 500Msps MAX101 flash ADCs. Both of these ADCs have a 50 input resistance and a 1.2GHz input bandwidth.
VIN RISO VOUT CL RL
High-Performance Video Distribution Amplifier
In a gain of +2 configuration, the MAX477 makes an excellent driver for back-terminated 75 video coaxial cables (Figure 8). The high output-current drive allows the attachment of up to six 2Vp-p, 150 loads to the MAX477 at +25C. With the output limited to 1Vp-p, the number of loads may double. The MAX4278 is a similar amplifier configured for a gain of +2 without the need for external gain-setting resistors. For multiple gain-of-2 video line drivers in a single package, see the MAX496/MAX497 data sheet.
Wide-Bandwidth Bessel Filter
Two high-impedance inputs allow the MAX477 to be used in all standard active filter topologies. The filter design is straightforward because the component values can be chosen independently of op amp bias. Figure 9 shows a wide-bandwidth, second-order Bessel filter using a multiple feedback topology. The component values are chosen for a gain of +2, a -3dB bandwidth of 10MHz, and a 28ns delay. Figure 10a shows a square-wave pulse response, and Figure 10b shows the filter's frequency response and delay. Notice the flat delay in the passband, which is characteristic of the Bessel filter.
MAX477
Figure 5. Capacitive-Load Driving Circuit
1 CL = 22pF 0 -1 GAIN (dB) -2 RISO = 20 -3 -4 -5 -6 1M 10M 100M CL = 100pF CL = 47pF
CL = 0pF
500
500
75 1G VIDEO IN
75 OUT1 75
MAX477
FREQUENCY (Hz)
Figure 6. Effect of CLOAD on Frequency Response With Isolation Resistor
500 500
75
75 OUT2 75
75
75 OUTN
MAX477
VIDEO IN
FLASH ADC (MAX100/MAX101)
75
Figure 7. Preamp for Video Digitizer
10
Figure 8. High-Performance Video Distribution Amplifier
______________________________________________________________________________________
300MHz High-Speed Op Amp
___________________Chip Information
TRANSISTOR COUNT: 175
602 301 VIN 100pF VOUT 110 20pF
MAX477
SUBSTRATE CONNECTED TO VEE
MAX477
Figure 9. 8MHz Bessel Filter
IN (100mV/div) 0.2V VOLTAGE (V) OUT (200mV/div) -0.2V
GND
GND
TIME (50ns/div)
Figure 10a. 5MHz Square Wave Input
10 8 6 4 GAIN (dB) 2 0 -2 -4 -6 -8 -10 1M 10M FREQUENCY (MHz) GAIN DELAY
48 38 28 18 8 -2 -12 -22 -32 -42 -52 100M DELAY (ns)
Figure 10b. Gain and Delay vs. Frequency
______________________________________________________________________________________ 11
300MHz High-Speed Op Amp MAX477
________________________________________________________Package Information
8LUMAXD.EPS
12
______________________________________________________________________________________
SOT5L.EPS

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