Here LM324 op-amp based instrumentation amplifier is designed and simulated using Multisim electronics design software. Single supply will be used in the design of the amplifier. The instrumentation amplifier is used in testing and measurement equipment to acquire small signal with noise. The working principle of instrumentation amplifier was explained in what is instrumentation amplifier & types of instrumentation circuits.
The circuit diagram of the LM324 op-amp based instrumentation amplifier using single supply of +5V is shown below.
Here the inputs to the amplifier circuit is biased using split resistor biasing. The resistors R8 and R9 are used to bias the input Vin1 at the midrange between the +5V and ground. Similarly the resistors R11 and R12 are used to bias the input Vin2 in the midrange of +5V and ground. The resistors R7 and R10 are used to create high impedance for the input signals. The capacitors C1 and C2 are used to reduce noise coming from the power supplies. This biasing is used in ac coupled non-inverting amplifiers see LM324 non-inverting amplifier.
The instrumentation amplifier gain is given by,
[A = frac{V_{out}}{V_{in2}-V_{in1}} = frac{R_{2}}{R_{1}}(1+frac{2 R_{f}}{R_{g}})]
where, (R_{f1} = R_{f2} = R_{f})
(R_{2} = R_{3}), (R_{1} = R_{4})
The oscilloscope display the input signal of 1mV and frequency of 1KHz and the output signal.
