EveryCircuit - Question

hurz

9 years ago

Solve the equation Vinput=Vout and this is only valid for one voltage.

Ajinkya_Mahajan

9 years ago

Thanks 😊😇

thebugger

9 years ago

It must have a feedback resistor, but yeah the output equals the input.

hurz

9 years ago

Were do you see the need of a resistor? No current no resistor to drop voltage. Ohms law.

erikjohanson2003

9 years ago

There will be an oscillation. It takes time for the inverter to invert whatever comes into it, so it is not a paradox.

hurz

9 years ago

There is no resistor needed and it also does NOT oscillate.

thebugger

9 years ago

Don't listen to him, it DOES need resistors in the feedback path, because you'll end up shunting the gate and rendering it disabled. The output gives you a direct connection to the input. The feedback resistors disable the direct connection and make the gate amplify and invert. Depending on the feedback resistors ratio the gate will have either voltage gain or current gain or both. You can view this as a inverting op amp amplifier. You need feedback resistors or you shunt the input to the output and render the op amp disabeld

thebugger

9 years ago

And eric is somewhat correct. If the gate has some hysteresis, which in reality is completely possible and the input has some parasitic capacitance, and there is a feedback resistor, there is a very real possibility that the gate can start oscillating.

hurz

9 years ago

Shunting the gate and rendering it disabled. Bullshit

hurz

9 years ago

The problem with this kind of voltage divider amp is a totaly different one in real, but lets see if you find out.

hurz

9 years ago

@erikjohanson2003, try to bring it to oscillation here in simulation. Good luck!

thebugger

9 years ago

If you short the output to the input you shunt the gate and it doesn't work anymore. The signal finds the easiest path from input to output and the gate just wastes power to try and negate the output, because it's an inverting gate and the output is 180dgs out of sync with the input.

hurz

9 years ago

Gate inputs impedance are almost infinite. Were does the current go? Anyway, take a sheet of paper and draw the transfer-function for output vs input voltage and see were they cross.

hurz

9 years ago

http://everycircuit.com/circuit/5344809107062784

hurz

9 years ago

The problem is NOT the path form output to input current. The problem is inside the gate current, cuz its like a class AB amp.

thebugger

9 years ago

No man you got me all wrong. A gate like this does you no good. You'll have to put an input signal. My scenario is when you actually put an AC source at the input. The gate will try to negate the source, because the output is inverted, thus only wasting current. http://everycircuit.com/circuit/6739517595189248

hurz

9 years ago

Yes, you got it all wrong. Check the circuit and description.

thebugger

9 years ago

Yeah but the gate is useless like so. Basically you omitt the input from the circuit and render it useless as a gate

hurz

9 years ago

Stabel supply voltage/2 can be very useful !