| 摘要 |
A buffer amplifier is disclosed which has the ability to retain a high voltage from input to output and is capable of coupling to highly capacitive loads. The input impedance can be tailored up to several hundred thousand ohms. The frequency range is from 0.5 Hz to 6 KHz for highly capacitive loads. The amplifier comprises, in combination, an input impedance matching stage and a first and a second amplification stage. The input impedance matching stage consists solely of passive components. The first amplification stage comprises an operational amplifier in series with a high voltage transistor. Circuitry associated with the transistor provides separate controllable AC and DC gains. The AC gain is fed back through a feedback loop to the op amp and does not contribute much to the overall AC gain of the stage, which is determined by two resistors. The DC gain is separately established and is used to set the proper biasing for the second amplification stage, which comprises a high voltage transistor connected in emitter follower configuration. The second amplification stage provides isolation and the capability of driving into highly capacitive loads.
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