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4 marksOperational Amplifiers

CAPE Physics Unit 2 · 2006 · Paper 2 · Question 6(d)(ii)

In the dark the resistance of the light-dependent resistor (ldr) is 400\text{ k}\Omega. Find the potential at the inverting terminal in this situation and use this value to explain why the light emitting diode (led) switches on.

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Other parts of this question

  1. 6(a)(i)Explain why the scales on the axes are logarithmic rather than linear.[1 mark]
  2. 6(a)(ii)What value does the graph give for the open loop gain of the op-amp.?[1 mark]
  3. 6(b)(i)Use the graph to determine its bandwidth.[1 mark]
  4. 6(b)(ii)Draw a circuit diagram to show how the non-inverting amplifier could be constructed.[2 marks]
  5. 6(b)(iii)Write the formula for the gain of this amplifier.[1 mark]
  6. 6(b)(iv)State the ratio of the feedback resistance to resistance of the input resistor in this non-inverting amplifier.[2 marks]
  7. 6(c)Using your answer to (a) above determine the maximum input voltage to the op-amp. if it is not saturated.[2 marks]
  8. 6(d)(i)Find the potential at the non-inverting terminal of the op-amp in Figure 8.[3 marks]
  9. 6(e)The led in the circuit is rated 2.4\text{ V}, 25\text{ mA}. A protective resistor has to be connected in series with it so that it does not burn out. What…[3 marks]

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