Swamping??

[rag's]

What is swamping of a transistor?What will happen to the gain of the transistor due to swamping??What happens to the distortion level??

 

[audioguru]

I think "swamping" happens when a transistor's input signal level is too high and it clips which makes horrible distortion.

A dictionary says, "to inundate, to burden, to overwhelm".

 

[3v0]

So swamping would be the same as overdriving a transistor?

EDIT: Or do we talk about swamping with analog signals and overdriving with digital.

 

[Torben]

So swamping would be the same as overdriving a transistor?

EDIT: Or do we talk about swamping with analog signals and overdriving with digital.

I thought the same thing--just another term for saturation or clipping. All About Circuits has a different explanation, though:



Of course I have no idea if that's what Rag's meant.



Torben

 

[audioguru]

I have used balancing emitter resistors with paralleled transistors but I have never called them swamping resistors like at All About Circuits.

An analog signal clips and produces severe distortion when the input signal level is too high.
A digital signal is already clipping so overdrive doesn't affect it.

A radio circuit is also "swamped" when the signal level is too high for it. Then it produces cross-modulation of the signals and they appear all over the dial.

 

[Mikebits]

I have heard of swamping resistors used in tuned circuits to broaden the bandpass.

 

[audioguru]

I have heard of swamping resistors used in tuned circuits to broaden the bandpass.

Yes, in the olden days in the IF of a stereo FM radio.
Crystal filters have replaced most tuned circuits now because the bandwidth is wide and flat and the skirts are very steep.

 

[Hero999]

I was having problems with a poor Internet speed and an engineer for the cable complany came round, made a few measurements and concluded that the signal was too strong so he increased the attenuation. Perhaps this was an example of swamping.

 

[audioguru]

I was having problems with a poor Internet speed and an engineer for the cable complany came round, made a few measurements and concluded that the signal was too strong so he increased the attenuation. Perhaps this was an example of swamping.

There are very many signals on my cable TV. About 50 analog TV stations, about 200 or 300 digital TV stations, about 50 HD TV statios, about 50 pay-per-view stations, about 100 radio channels and high speed internet.

If the signal is too strong then the poor receiver will have cross-modulation of all those signals plus cross-modulation of the harmonics of all those signals.

 

[BeeBop]

What is swamping of a transistor?What will happen to the gain of the transistor due to swamping??What happens to the distortion level??

According to Floyd (Electronic Devices 7th ed.) swamping is a technique of using a partially bypassed emitter resistor to stabilize voltage gain. It reduces the effects of R prime emitter (internal emitter resistance of the transistor, which varies with temperature and emitter current.)
In this cct, both emitter resistors affect the dc bias, while only Re1 affects the ac voltage gain. So for gain, rather than Av=Rc/r'e+Re1 you have Av=Rc/Re.