Question

Q3 (a) State the properties of an ideal opamp. Give one reason why the assumption that an opamp is ideal is useful when calculating the behaviour of circuits containing opamps? Figure Q3 shows the circuit diagram of an amplifier constructed using an ideal opamp. State the value of the voltage v appearing at the inverting input of the opamp. Clearly state what properties of an ideal opamp you are assuming (c) Hence calculate the currents flowing through the resistors RA, RB and Rf. Clearly state what properties of a perfect opamp you are assuming OUT Figure Q.3 (d) Hence derive an expression for the output voltage vour as a function of the input voltages, V and VB (e) Choose values for the resistors so that the output is given by

(a) State the properties of an ideal opamp. Give one reason why the assumption that an opamp is ideal is useful when calculating the behaviour of circuits containing opamps? [3]

(b) Figure Q3 shows the circuit diagram of an amplifier constructed using an ideal opamp. State the value of the voltage v– appearing at the inverting input of the opamp. Clearly state what properties of an ideal opamp you are assuming. [2]

(c) Hence calculate the currents flowing through the resistors RA, RB and RF. Clearly state what properties of a perfect opamp you are assuming [4]

Figure Q3 (d) Hence derive an expression for the output voltage vOUT as a function of the input voltages, VA and VB. [4]

(e) Choose values for the resistors so that the output is given by vOUT = −3VA − 0.5VB [4]

Answer 1

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