Non Switching Amps
- Thread starter Rybeam
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In the conventional amplifier push pull circuits when the NPN transistor is driving on it's half of the waveform, the PNP transistor is inadvertently turned (switched) off completely by the signal, and vice-versa.
When either of the output transistors is turned off, not even the bias current flows, and it takes time to turn the transistor back on as the signal swings to the other half of the cycle.. This adds distortion. IIAC this is more noticable at very low signal levels because it occurs where the signal reverses polarity, and to add insult to injury, the distortion tends to be high frequency spikes.
The non switching amplifier circuit sort of chops off the other half of the signal ON THAT SIDE so that the turn off (switch off) of the transistor doesn't happen and the bias current continues to flow. This results in significantly lower distortion.
Clear as mud?
When either of the output transistors is turned off, not even the bias current flows, and it takes time to turn the transistor back on as the signal swings to the other half of the cycle.. This adds distortion. IIAC this is more noticable at very low signal levels because it occurs where the signal reverses polarity, and to add insult to injury, the distortion tends to be high frequency spikes.
The non switching amplifier circuit sort of chops off the other half of the signal ON THAT SIDE so that the turn off (switch off) of the transistor doesn't happen and the bias current continues to flow. This results in significantly lower distortion.
Clear as mud?
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calman46 said:
With or without the non-switching circuit, the output of most amplifiers is a combination of the work of TWO circuits, the positive swinging driver/output circuit, and the negative swinging driver/output circuit.
It's just that with the non-switching circuit, they play with each other a little better...
As evidenced by the significantly lower distortion figures.
Of the Pioneer amps I am aware of, the ones with the non-switching circuits have the lowest distortion specs.
sbparks
Active Member
Mark,
I've been wondering how a transistor (actually a transistor pair) would act as an amplifier, so you've given me (us) a glimpse into how these circuits work. So, that's a good start. And you're right, it is about as clear as mud, but it is a start.
Can you add to the muddiness and give me a glimpse into how the tube amplifiers do their job... Does a tube act as a switch like a transistor does?
I know this is a very general question, but maybe we can work it down to more specific questions and we can all learn.
Thanks.
I've been wondering how a transistor (actually a transistor pair) would act as an amplifier, so you've given me (us) a glimpse into how these circuits work. So, that's a good start. And you're right, it is about as clear as mud, but it is a start.
Can you add to the muddiness and give me a glimpse into how the tube amplifiers do their job... Does a tube act as a switch like a transistor does?
I know this is a very general question, but maybe we can work it down to more specific questions and we can all learn.
Thanks.
sbparks said:
Basically any amplifier (tube or transistor or RELAY or whatever) works on the principle of a smaller signal controlling a larger one. The rest is details... a LOT of details. There are plenty of websites, articles and tutorials out there that can do a far better job than I can in explaining them. So many in fact that I hesitate to try to recommend some. There are however a HUGE number of links at http://101science.com/transistor.htm ...... enjoy....
I just answered one obscure question about one involved detail in one particular type of amplifier circuit used by a specific manufacturer across it's product line....
