# Tag Info

## New answers tagged operational-amplifier

### What is the source of noise in this AD620/OP490 EEG circuit?

Without knowing how your actual circuit is built, it is going to be nearly impossible to help you to track down the origin of the noise you are observing. Is it wired up on a breadboard? Are you using ...

### What is the source of noise in this AD620/OP490 EEG circuit?

Your circuit is missing decoupling capacitors on all integrated circuits. You have unconnected op-amps in your OP-490. The unconnected op-amps can pick up noise from the environment. They may also ...
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### Why make second stage current larger than input stage current in op-amp?

The maximum current available for charging and discharging Cc is either the first stage current or the second stage current, whichever is smallest of the two. So the slew-rate roughly depends on the ...
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### Why is one op-amp in my circuit messing up the other?

Intuitively, R1 and R5 both pass the same current, and by Ohm's law that means R1 drops over $\frac{2}{3}$ of the signal. The same goes for R2 and R6, and this is why the signals appearing at ...
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### Current flow in non-inverting op-amp amplifier

There are a couple of points that make things much easier: Current doesn't flow into or out of the op-amps inputs, because they have infinite impedance. It's as if the op-amp isn't even there. With ...
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### Why is one op-amp in my circuit messing up the other?

When you insert the 3rd op-amp (diff) the first series resistors (R1, R2) become part of the 3rd op-amp's active circuit. Remove the first set of series resistors. If you really want the extra 10K of ...
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### Finding poles by inspection - 2 resistors

Is this correct? Yes, that is correct; R2 feeds a virtual ground hence it acts like a resistor to 0 volts. Then, if you Thevenise R1 and R2 to find the effective resistance of the source (Vin) you ...
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### Op-amp - audio starts only after a few seconds

Try adding a 100nF capacitor in series with the input. There may be a large value capacitor in the source that has to charge in order to allow your op-amp to reach bias, since your amplifier is DC-...
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### Is there also equal voltage on the inputs of an op-amp with a capacitor in the feedback rather than a resistor?

First of all, in your diagram, the current through and voltage across the feedback capacitor are in correct. See my diagram. simulate this circuit – Schematic created using CircuitLab The ...
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### Negative feedback divider calculation for NE5532

Step 1: Convert the desired dB values to voltage ratios. For example, voltage gain of 6dB is a ratio of 2:1. Step 2: Calculate the values for each desired gain value. Ignore the switch for now - you ...
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### Differential pair with active load including resistance

Your question about why the tail node is a small signal ground is equally valid for the simple amplifier with a current mirror load. Because that circuit is also not fully symmetrical to be split into ...
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### Op-amp output as gate voltage to MOSFET

The MOSFET is always in the triode region. The constant current is not a result of the MOSFET being in the saturation region, but a result of the closed-loop system controlling the MOSFET gate. When ...
• 342k
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### Op-amp output as gate voltage to MOSFET

To meet the "demand" under more strenuous operating conditions, the MOSFET gate has to be driven with a progressively higher voltage. In other words, the change from MOSFET saturation region ...
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