small op-amp problem, please help me

[vicky29]

double op-amp

Hi friends,
Recently in a op-amp book i read feeding an analog input to a non-inverting pin of a op-amp is not a good idea and less accurate than if feed to inverting pin. Actually i need to amplify a analog voltage from 0 to 0.5 volts to 0 to 5 volts for which i used the single opamp circuit as shown below. should i use double op-amp circuit )also as shown below) for more accuracy) first stage of opamp is a inverter with GAIN=-1 and second one is with Gain = -10.
Thanks

 

[sunking]

Without buffer is better, at least for low power and low offset

 

[nandu_r]

if your amplifier has a high input inpedance, there is no point in adding a buffer in this circuit

 

[htrs]

Please refer the website www.designinganalogchips.com and download the ebook.

 

[dinow]

try the sedra book for microelectronic circuits, very informative

 

[Kral]

Vicky29
The main advantage to the non-inverting configuration, as shown in your first crcuit, is high input impedance. The input imedance is equal to the open loop input impedance of the op-amp times the loop gain. One disadvantage is that the common mode rejection ratio must be taken into consideration, since the op-amp input does not stay at virtual ground. I see no advantage to your 2nd circuit. You are going to amplify any errors incurred in the first stage by the gain of the 2nd stage. Also the input impedance of the 2nd circuit is 10K, vs darn near infinity for the 1st circuit.
Regards,
Kral