LT1010 APPLICATIONS INFORMATION This is a good example of how fast op amps can be made stage. Feedback is arranged in the conventional manner, quite easy to use by employing an output buffer. although the 68µF-0.01µF combination limits DC gain to unity for all gain settings. For applications sensitive to Integrator NTSC requirements, dropping the 25Ω output stage bias A lowpass amplifier can be formed just by using large C value will aid performance. F in the inverter described earlier, as long as the increasing R2 closed-loop output impedance above the cutoff frequency 800Ω is not a problem and the op amp is capable of supplying the required current at the summing junction. C1 15pF – A1 A2 CI HA2625 LT1010 VOUT 1010 AI09 I V + IN IN RF 20k R1 100Ω – A1 A2 LT1012 LT1010 VOUT 1010 AI07 + This shows the buffer being used with a wideband ampli- CF fier that is not unity-gain stable. In this case, C1 cannot 500pF be used to isolate large capacitive loads. Instead, it has an optimum value for a limited range of load capacitances. If the integrating capacitor must be driven from the buffer The buffer can cause stability problems in circuits like this. output, the circuit above can be used to provide capacitive With the TO-220 packages, behavior can be improved by load isolation. As before, the stability with large capacitive raising the quiescent current with a 20Ω resistor from the loads is determined by RFCF . bias terminal to V+. Alternately, devices in the miniDIP can Wideband Amplifiers be operated in parallel. This simple circuit provides an adjustable gain video It is possible to improve capacitive load stability by oper- amplifier that will drive 1V ating the buffer class A at high frequencies. This is done P-P into 75Ω. The differential pair provides gain with the LT1010 serving as an output by using quiescent current boost and bypassing the bias terminal to V– with more than 0.02µF. 15V TYPICAL SPECIFICATIONS R2 1VP-P INTO 75Ω 1.6k AT A = 2 8.2k 25Ω 0.5dB TO 10MHz 3dB DOWN AT 16MHz + AT A = 10 – BIAS 0.5dB TO 4MHz A1 A2 22µF + OUTPUT 22µF –3dB = 8MHz HA2625 LT1010 1010 AI10 INPUT + LT1010 OUTPUT (75Ω) R1 400Ω –15V PEAKING 5pF to 25pF 900Ω Putting the buffer outside the feedback loop as shown INPUT Q1 Q2 here will give capacitive load isolation, with large output 1k Q1, Q2: 2N3866 capacitors only reducing bandwidth. Buffer offset, referred GAIN SET 5.1k + to the op amp input, is divided by the gain. If the load re- 0.01µF 68µF sistance is known, gain error is determined by the output –15V resistance tolerance. Distortion is low. 1010 AI08 1010fe 10 Document Outline Fteatures Applications Description Typical Application Absolute Maximum Ratings Preconditioning Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Applications Information Schematic Diagram Definition Of Terms Package Description Revision History Related Parts
