# op amp questionsHi

Discussion in 'Homework Help' started by Kayne, Aug 21, 2011.

1. ### Kayne Thread Starter Active Member

Mar 19, 2009
105
0
Hi,

I wanted to check some answers for the question that are in the attachement. There are 3 question A,B,C which answers are povided below

A.

Temp change of 24dC
Temp coefficient of input offset = 15uV/dC

$24*15*10^{-6} = 0.36V$

$gain = \frac{2.2*10^6+10*10^{3}}{10*10^{3}} = 221$

$221 *2*10^{-{3}} = 0.442$

So the variation is

$0.442 - 0.36 = 0.082V$

B.
input offset voltage = 0.69mV

$voltage gain =\frac{ 1*10^6+10*10^{6}}{10*10^{6}} = 101$

error voltage at output

$101*0.69*10^{-3}= 0.06969V$

so the error voltage at the output is 0.06969V

C.

Amp gain = 668
Resistor = 32k
input offset current = 7.3nA

$Vin = IR = 7.3*10^{-9} * 32*10^{3}= 0.0002336V$

So the error voltage at the output is

$Voutput = gain * Vin = 668* 0.0002336 = 0.156044V$

So the error voltage at the output is 156mV

Thanks for your time and help
Kayne

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2. ### praondevou AAC Fanatic!

Jul 9, 2011
2,936
489
1. question:

gain is 220. Rfeedback/Rin. gives you a variation of 79.2mV