This is a design for a high impedance DC voltmeter. This circuit is design with built by uA741 IC. This IC is a op-amp non-inverting DC amplifier. The IC have negative feedback that is through a DC meter requiring 1mA for full scale deflection. This is the figure of the circuit.
The principle work of this circuit is since R6 is 100 Ohms, the meter will show full scale reading when the DC input voltage to pin3 is equal to the voltage drop across R6, viz 0.1 volts. Choice of R1 and R2 for getting different voltage ranges are shown in the table. The diodes D1 and D2 protect the IC from accidental excessive input voltages and diodes D3 and D4 protect the meter from overloads. The circuit can be powered from a +9V/-9V dual power supply.
The meter M1 can be a 1mA FSD DC ammeter. The values of R1 & R2 for different voltage ranges can be obtained from the table is given below.
The principle work of this circuit is since R6 is 100 Ohms, the meter will show full scale reading when the DC input voltage to pin3 is equal to the voltage drop across R6, viz 0.1 volts. Choice of R1 and R2 for getting different voltage ranges are shown in the table. The diodes D1 and D2 protect the IC from accidental excessive input voltages and diodes D3 and D4 protect the meter from overloads. The circuit can be powered from a +9V/-9V dual power supply.
The meter M1 can be a 1mA FSD DC ammeter. The values of R1 & R2 for different voltage ranges can be obtained from the table is given below.
