# Op Amps - non-inverting

Discussion in 'Electronics Homework Help' started by JasonMcG, Jun 6, 2014.

1. ### JasonMcG

9
0
Mar 2, 2014
Hi

Need help with the following problem and how to go about it.

Consider a non- inverting amplifier circuit of a closed loop gain of 48. The input to the amplifier is an ac input signal of 100 mV at 1 kHz. The non-inverting amplifier is implemented using the LM 324 and the device parameters are specified to be: Aol = 100 V/mV; Vio = 7.0 mV, IIB = 300 nA, Iio = 100 nA, and SR = 0.4 V/μS. Given that the input resistor is 10 kΩ, and the power supply is ±15 V, do the following:
i) For an uncompensated design, determine the output voltage and the maximum dc offset error at the output of the amplifier. [5]
ii) Determine the magnitude of the offset minimizing resistor. [2]
iii) For a compensated design, determine the maximum frequency of the input voltage for which the output is not slew rated. Assume that the effect of error due to input offset current on the peak output voltage can be neglected.

Regards
Jason

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
Excellent question.

Show us how far you've progressed.

3. ### LvW

604
146
Apr 12, 2014
Jason, before starting to solve the task you have to be informed about the meaning of the various mentioned parameters (Aol, IIB, Iio, SR, compensared/uncompensated). Are you?

4. ### JasonMcG

9
0
Mar 2, 2014
Aol is your open loop gain.
Vio is your input offset voltage.
Iib is your input bias current.
Iio is your input offset current.

For i) I found Vo(vio) to be 48 * 7mV = 336mV.
Not sure if this is correct.

I'm not looking for answers but ways to go about solving this problem and op amp problems in general as I am looking to learn

5,164
1,087
Dec 18, 2013
Hi Jason
So first thing to do is work out your gain setting resistors. So have you been told how to do this?

6. ### JasonMcG

9
0
Mar 2, 2014
No I'm not sure how to do that

7. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
Perhaps you can start with a drawing of a non-inverting amplifier with just an op-amp and two resistors. You're familiar with that, right?

Then check your notes for diagrams where these two resistors labelled Ra and Rb, or R1 and R2 (or similar) and where you have also noted a formula that involves either the ratio between them, or the ratio of one to the sum of both.