A-LevelPhysicsD.C. circuits9702/42 · Feb/Mar 2019 · Q79 Marks
Two properties that an ideal operational amplifier (op-amp) would have are constant voltage gain and infinite slew rate. State what is meant by: gain of an amplifier
- (a)(i)Two properties that an ideal operational amplifier (op-amp) would have are constant voltage gain and infinite slew rate. State what is meant by: gain of an amplifier[1]
- (a)(ii)infinite slew rate.[2]
- (b)(i)The partially completed circuit of a non-inverting amplifier, incorporating an ideal op-amp, is shown in Fig. 7.1. On Fig. 7.1, complete the circuit for the non-inverting amplifier. [Figure 7.1][2]
- (b)(ii)For the completed circuit of Fig. 7.1, the gain of the amplifier is 25. The resistance of resistor R₁ is 12kΩ. Calculate the resistance of resistor R₂.[2]
- (b)(iii)Calculate, for the amplifier gain of 25, the range of values of V_IN for which the amplifier does not saturate.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2019). The mark or mark type is shown in brackets.
- [B1] output voltage / input voltage
- [B1] no time delay between input and output
- [B1] clear reference to change(s) in input and / or output
- [B1] V_IN only connected to non-inverting input
- [B1] midpoint between R1 and R2 only connected to inverting input
- [C1] gain = 1 + (R₁/R₂); 25 = 1 + (12 × 10³)/R₂
- [A1] R₂ = 500 Ω
- [C1] V_MAX = 9/25 = 0.36 V
- [A1] range is -0.36 V to + 0.36 V
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →