Importance of active and passive feedback and advantages

[hari_preetha]

What is the importance of active and passive feedback and advantages

 

[Audioguru]

I do not know what is "passive feedback".
Active feedback is used as positive feedback in an oscillator or to make very fast Schmitt Trigger switching.
Active feedback is also used as negative feedback in a transistor or opamp amplifier to reduce distortion and increase high frequency response.

 

[hari_preetha]

Active feedback , one transistor below and another transistor is connected feedback to the below transistor in cascade fashion. What is the importance of the one transistor below other transistor is above connected feedback to the below transistor , what is the importance of this kind of two transistors connecting in high frequency in terms of more than 1GHz( RF range).
I don't know exact meaning of "passive biasing", I wanted to ask the feedback elements used as L,C,R to the transistor, what is this kind of feedback in high frequency response in terms of more than 1GHz.

 

[Audioguru]

One transistor is connected below in a cascode circuit. I do not know what you are talking about when you said "cascade fashion". Please post the schematic.
Biasing is almost always "passive".

 

[hari_preetha]

One transistor is connected below in a cascode circuit. I do not know what you are talking about when you said "cascade fashion". Please post the schematic

Herewith I attached the schematic

 

[Audioguru]

Your schematic is similar to this microphone preamp:

 

[hari_preetha]

Yes,similar that microphone preamp in microwave frequency range( > 1GHz).

 

[hari_preetha]

Active feedback is used as positive feedback in an oscillator or to make very fast Schmitt Trigger switching.Active feedback is also used as negative feedback in a transistor or opamp amplifier to reduce distortion and increase high frequency response.

Is any other advantages of active feedback.

 

[FvM]

I don't think that the DC feedback in the microphone preamplifier is "similar" to the circuit in post #5.

While the microphone preamplifier uses feedback for bias point stabilization but cancels feedback for signal frequency, your circuit effectively shorts the input signal. I don't see any practical purpose of this circuit if it's intended as amplifier. May be for some kind of signal clamping.

 

[LvW]

I do not know what is "passive feedback".
Active feedback is used as positive feedback in an oscillator or to make very fast Schmitt Trigger switching.
Active feedback is also used as negative feedback in a transistor or opamp amplifier to reduce distortion and increase high frequency response.

*Passive feedback means: Feedback circuitry contains passive parts only; this applies to positive as well as negative feedback.
*Active feedback: Feedback path contains active elements.
Example: Phase-compensated non-inverting Miller-integrator. Here, we have an inverting feedback path consisting of the integrating capacitor in series with an active opamp inverter (gain "-1") - both connected to the non-inverting terminal of the main opamp.

 

[hari_preetha]

your circuit effectively shorts the input signal. I don't see any practical purpose of this circuit if it's intended as amplifier.

Which circuit shorts the input signal, posting # 5 circuit or posting 6, Can you clarify it.

I didn't get the answer for importance of active and passive feedback and also advantages of them.

 

[FvM]

Which circuit shorts the input signal, posting # 5 circuit or posting 6, Can you clarify it.

Obviously the post #5 circuit.

 

[hari_preetha]

Obviously the post #5 circuit.

But in the simulation, it is not shorted,it worked fine. I didn't know,what about the in the PCB board. How it is shorting, can you justify it posting # 5 Circuit.

 

[FvM]

But in the simulation, it is not shorted,it worked fine.

Working fine for which purpose? Can you show the simulation setup?

 

[D.A.(Tony)Stewart]

#5 regulates a constant current on Rc based on Vc=(Vcc-Vbe*2)/Rc and present a low input Impedance to an AC coupled input.

 

[hari_preetha]

Working fine for which purpose? Can you show the simulation setup?

That active feedback concept is taken for design of low noise amplifier, it is accepted in the one of the IEEE journal paper. Screen shot shows the implemented IEEE journal paper active feedback concept, whatever it is shown in the posting #5.