Datasheet LT1192 (Analog Devices) - 8
| Hersteller | Analog Devices |
| Beschreibung | Ultrahigh Speed Operational Amplifier |
| Seiten / Seite | 12 / 8 — APPLICATIO S I FOR ATIO. Double Terminated Cable Driver. Settling Time … |
| Dateiformat / Größe | PDF / 259 Kb |
| Dokumentensprache | Englisch |
APPLICATIO S I FOR ATIO. Double Terminated Cable Driver. Settling Time Poor Bypass. Cable Driver Voltage Gain vs Frequency
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LT1192
U U W U APPLICATIO S I FOR ATIO Double Terminated Cable Driver
amplified to 1mV/DIV the settling time to 1mV is 4.132µs 5V for the 0.1µF bypass; the time drops to 140ns with multiple 3 + 7 75Ω CABLE 6 bypass capacitors. LT1192 2 – 4 R 75 FB Ω RG –5V
Settling Time Poor Bypass Cable Driver Voltage Gain vs Frequency
24 TA = 25°C A = +10 V R = 910 FB Ω 20 V R = 47 OUT G Ω VOUT 0V 0V AV = +5 1V/DIV 1mV/DIV RFB = 910Ω 16 RG = 100Ω 12 8 LT1192 • TA05 4 CLOSED LOOP VOLTAGE GAIN (dB) SETTLING TIME TO 1mV, AV = –1 SUPPLY BYPASS CAPACITORS = 0.1µF 0100k 1M 10M 100M
Settling Time Good Bypass
FREQUENCY (Hz) LT1192 • TA07 energy. The best performance can be obtained by double termination (75Ω in series with the output of the ampli- fier, and 75Ω to ground at the other end of the cable). This termination is preferred because reflected energy is VOUT VOUT 0V 0V 1mV/DIV absorbed at each end of the cable. When using the double 1V/DIV termination technique it is important to note that the signal is attenuated by a factor of 2, or 6dB. For a cable driver with a gain of 5 (op amp gain of 10) the – 3dB bandwidth is 56MHz with only 0.25dB of peaking. LT1192 • TA06 SETTLING TIME TO 1mV, A
Using the Shutdown Feature
V = –1 SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM The LT1192 has a unique feature that allows the amplifier
Cable Terminations
to be shut down for conserving power or for multiplexing several amplifiers onto a common cable. The amplifier will The LT1192 operational amplifier has been optimized as a shut down by taking Pin 5 to V–. In shutdown, the amplifier low cost video cable driver. The ±50mA guaranteed output dissipates 15mW while maintaining a true high impedance current enables the LT1192 to easily deliver 7.5VP-P into output state of 15kΩ in parallel with the feedback resis- 100Ω, while operating on ±5V supplies or 2.6VP-P on a tors. The amplifiers must be used in a noninverting con- single 5V supply. figuration for MUX applications. In inverting configura- When driving a cable it is important to terminate the cable tions the input signal is fed to the output through the to avoid unwanted reflections. This can be done in one of feedback components. When the output is loaded with as two ways: single termination or double termination. With little as 1kΩ from the amplifier’s feedback resistors, the single termination, the cable must be terminated at the amplifier shuts off in 400ns. This shutoff can be under the receiving end (75Ω to ground) to absorb unwanted control of HC CMOS operating between 0V and – 5V. 8
U U W U APPLICATIO S I FOR ATIO Double Terminated Cable Driver
amplified to 1mV/DIV the settling time to 1mV is 4.132µs 5V for the 0.1µF bypass; the time drops to 140ns with multiple 3 + 7 75Ω CABLE 6 bypass capacitors. LT1192 2 – 4 R 75 FB Ω RG –5V
Settling Time Poor Bypass Cable Driver Voltage Gain vs Frequency
24 TA = 25°C A = +10 V R = 910 FB Ω 20 V R = 47 OUT G Ω VOUT 0V 0V AV = +5 1V/DIV 1mV/DIV RFB = 910Ω 16 RG = 100Ω 12 8 LT1192 • TA05 4 CLOSED LOOP VOLTAGE GAIN (dB) SETTLING TIME TO 1mV, AV = –1 SUPPLY BYPASS CAPACITORS = 0.1µF 0100k 1M 10M 100M
Settling Time Good Bypass
FREQUENCY (Hz) LT1192 • TA07 energy. The best performance can be obtained by double termination (75Ω in series with the output of the ampli- fier, and 75Ω to ground at the other end of the cable). This termination is preferred because reflected energy is VOUT VOUT 0V 0V 1mV/DIV absorbed at each end of the cable. When using the double 1V/DIV termination technique it is important to note that the signal is attenuated by a factor of 2, or 6dB. For a cable driver with a gain of 5 (op amp gain of 10) the – 3dB bandwidth is 56MHz with only 0.25dB of peaking. LT1192 • TA06 SETTLING TIME TO 1mV, A
Using the Shutdown Feature
V = –1 SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM The LT1192 has a unique feature that allows the amplifier
Cable Terminations
to be shut down for conserving power or for multiplexing several amplifiers onto a common cable. The amplifier will The LT1192 operational amplifier has been optimized as a shut down by taking Pin 5 to V–. In shutdown, the amplifier low cost video cable driver. The ±50mA guaranteed output dissipates 15mW while maintaining a true high impedance current enables the LT1192 to easily deliver 7.5VP-P into output state of 15kΩ in parallel with the feedback resis- 100Ω, while operating on ±5V supplies or 2.6VP-P on a tors. The amplifiers must be used in a noninverting con- single 5V supply. figuration for MUX applications. In inverting configura- When driving a cable it is important to terminate the cable tions the input signal is fed to the output through the to avoid unwanted reflections. This can be done in one of feedback components. When the output is loaded with as two ways: single termination or double termination. With little as 1kΩ from the amplifier’s feedback resistors, the single termination, the cable must be terminated at the amplifier shuts off in 400ns. This shutoff can be under the receiving end (75Ω to ground) to absorb unwanted control of HC CMOS operating between 0V and – 5V. 8