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Tuesday, November 03, 2015

Digital gain control of Opamp

The gain of U1 can be controlled by a digital binary 1248 nibble at ABC. The gain at digital 000 is unity or 1 and the gain at various stages are set by 4051.

Precision Attenuator with Digital Control - delabs

There are eight different gains as the steps of gain resistor network is chosen by 4051. The on resistance of 4051 channel around 100E gets added to U1 pin 2 internal impedance.

Digital gain control of Opamp.

Auto ranging 4-1/2 Digit Digital Voltmeter - delabs

You can use separate resistor networks with trimpots for each channel if you require but keep the networks total burden on U1 pin 6 to around 10K, not less than than. You can use this to set the gain of a amplifier with the help of a microcontroller.

If you have any IC with Analog FET Switches, you can adapt this design for that. The Cross-talk should be less and On-Resistance as low as Possible. Off Resistance as High as possible.