Calculated Gain Doesn't Match Simulation

Jan 20, 2007 5 Replies

I am simulating a differential circuit with a calculated gain of 1000 (10M/1k) but when I run it in the simulator I only get a gain of about



15 (15 mV over 1 mV input). I'm using a TL081 in a non-inverting configuration, the feedback resistor is 10M and the input resistor is
10k. What am I doing wrong?

Post your schematic on A.B.S.E or a URL link.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

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Without looking at your circuit, my guest is that you don't have enough current feeding back to the op-amp. Try dropping the resistors and/or using two stages.

With the info you provided for all we know you could have a path the length of the Chartres Labyrinth dropping your gain. provide schematic for any helpful assistance.

BTW wouldn't "The Chartres Labyrinth" make a nifty looking spiral inductor on a pcb...

maybe aa a delay line, all that doubling back would reduce its inductance

Bye. Jasen

Or maybe a folded antenna for vhf/uhf on a circuit board...saves a lot of space.

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