[SI-LIST] Re: operational amplifiers

  • From: steve weir <weirsp@xxxxxxxxxx>
  • To: zhang_kun@xxxxxxxxxx, si-list <si-list@xxxxxxxxxxxxx>
  • Date: Wed, 08 Oct 2003 01:01:08 -0700

Zhangkun, if you mismatch the driving impedance then you will see a 
corresponding shift in offset voltage due to the bias current of the 
Op-Amp.  For CMOS inputs, the current is very low, and a difference of 45K 
may mean a lot less error than say contamination on the PCB.  But, if you 
are using a bipolar device, 45K may translate to a number of mV 
offset.  You just have to plug those numbers into your error budget and see 
where you end up.

Regards,


Steve.
At 10:40 AM 10/8/2003 +0800, Zhangkun wrote:
>Dear All:
>We are doing some simulation about operational amplifiers. I have one 
>question about the input of operational amplifiers. If the input impedance 
>of inverting input and non-inverting input are not same, does the 
>operational amplifiers work normally?
>
>For example, the resistor between vin- and inverting input of operational 
>amplifiers is 5K ohm and the resistor between vin+ and non-inverting input 
>of operational amplifiers is 50K ohm. Will the operational amplifier work 
>normally?
>
>Best Regards
>
>Zhangkun
>2003.10.08
>
>
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