Current - or voltage amplifier is a high speed and with a low noise.

摘要

A low noise, high speed current transimpedance amplifier system (20) includes AC bootstrapping for the photodiode D1 by capacitor C2 connected between the source of the JFET Q1 and the cathode of the photodiode D1 by line (56). Line (58) also provides AC bootstrapping to the case of the module (40) through capacitor C2. Similarly, the source resistor R3 and drain of JFET Q1 are AC bootstrapped through capacitors C1 and C4 to the emitters of the transistors Q2 and Q4 by lines (60) and (62). The collectors of the second stage transistors Q2 and Q4 are bootstrapped to the third stage transistor Q3 emitter through capacitor C8 by line (64). This bootstrapping reduces the effective input capacitance at the front end of the amplifier system (20) by a factor of up to about 100, thus reducing signal noise component in the subsequent stage or stages to negligible compared to front end noise.