0
\$\begingroup\$

I just wondering how do you calculate the gain of the amplifier in a circuit like this:MAX446 CHIP

I am familiar with gain calculation on non-inverting and inverting opamp but am having trouble with this.

Any help would be appreciated.

\$\endgroup\$
1
\$\begingroup\$

This is actually a non-inverting op-amp with a pass band filter and a DC offset cancellation.

The formula is

Av = 1 + R2 / R1

Where the resistor are the 100k and 10k, so you would get a gain of 11.

  • The first group with 1 cap and 2 1Mohm resistor are a high pass filter and decoupling.
  • The 100pF below the chip is a low pass filter.
  • The 1uF below the 10k resistor is there to remove DC offset.
\$\endgroup\$
  • \$\begingroup\$ so that means that it will always have a 2.5v input? \$\endgroup\$ – Newbie Sep 30 '18 at 1:21
  • \$\begingroup\$ If the input bias current is zero (the input ESD structures have low leakage, and the input transistor is JFET or MOSFET), then YES. \$\endgroup\$ – analogsystemsrf Sep 30 '18 at 1:54
  • \$\begingroup\$ @analogsystemsrf wouldn't that mean that the output will always be 27.2V? \$\endgroup\$ – Newbie Sep 30 '18 at 2:12
  • \$\begingroup\$ That's the purpose of the 1uF cap, to remove DC offset, so only the signal will be amplified. I guess this is a solution to be able to use a single rail supply. The output cannot be higher than the opamp supply voltage. \$\endgroup\$ – Damien Sep 30 '18 at 2:15
  • \$\begingroup\$ @Damien so just to be clear this circuit can be used to amplifier the human voice to used in an ADC? \$\endgroup\$ – Newbie Sep 30 '18 at 2:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.