Internal circuit schematic of integrated program-controlled measurement amplifier circuit chip LH0084

Programmed measurement amplifiers have analog switches and drive circuits added to the measurement amplifier. Gain selection switches S1-S'l, S2-S'2, S3-S'3 operate in pairs. Only one switch is closed at each moment. When changing the digital input code, the closed switch number can be changed. Different feedback resistors are equivalent to automatically changing the resistance of the potentiometer R1 in the measurement amplifier to achieve the purpose of changing the gain of the amplifier.

The following figure shows the internal circuit schematic of the integrated program-controlled measurement amplifier circuit chip LH0084. On the one hand, the feedback amplifier of the operational amplifier A3 is selected by wiring to determine the basic amplification factor of the amplifier, and on the other hand, the analog switch is controlled to achieve automatic control of the amplification factor.