# op amp questionsHi

#### Kayne

Joined Mar 19, 2009
105
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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#### praondevou

Joined Jul 9, 2011
2,942
1. question:

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