Fig. 8.1 shows a circuit containing an ideal operational amplifier (op-amp). The op-amp is supplied with $+9\,\text{V} / -9\,\text{V}$. A voltmeter with range $0 - 5.0\,\text{V}$ is used to measure the amplifier output. A switch allows the inverting input of the op-amp to be linked to either resistor $R_A$ or resistor $R_B$.
(a)[1]
A positive potential $+V_{IN}$ is applied to the circuit input. On Fig. 8.1, place P on the positive side of the voltmeter so that the meter gives a positive reading.
(b(i))[2]
Calculate the potential $V_{IN}$ so that the voltmeter gives full-scale deflection when the inverting input of the op-amp is connected to resistor $R_A$ with resistance $100\,\Omega$.
(b(ii))[1]
Calculate the potential $V_{IN}$ so that the voltmeter gives full-scale deflection when the inverting input of the op-amp is connected to resistor $R_B$ with resistance $10\,\text{k}\Omega$.
(c)[1]
Suggest a use for this kind of circuit.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “P on the link between the earth symbol and the voltmeter” …