DC amplifier with voltage input and current output - has two operational amplifier stages with output transistor in each stage

摘要

The proposed circuit facilitates changing the operating point, e.g. the gain, without the necessity for trimming and balancing the complete amplifier. Input and output are referred to zero volts. The amplifier is divided into two stages, each containing an operational amplifier. The stages operate with opposite polarity. The first stage output is connected to the high impedance input of a transistor, typically a FET, connected across the power supply. This transistor applies a voltage proportional to the input voltage to the second stage. The second stage output is similarly loaded with a transistor. The output into the load is a current proportional to the input voltage which is independent of the load resistance over a wide range.