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electronic mind said:but what i know is that Zener Diode is used for keeping the voltage drop across it constant..... then how can it be noisy...
electronic mind said:aha...
thanx a lot
but still one thing .... what about the 22k resistor does it have anything to do with the noise generating or just a feed back
The gain is reduced if the source impedance is significant. However, since the source impedance is only a few ohms, the mid-band gain is actually not affected much by the feedback resistor. What IS affected is the bandwidth (low frequency corner). The feedback lowers the input resistance. Simulation shows the low frequency corner to be about 16kHz! Not very useful if you want audio noise. The input cap needs to be increased to at least 10uF if audio noise is desired.Nigel Goodwin said:electronic mind said:aha...
thanx a lot
but still one thing .... what about the 22k resistor does it have anything to do with the noise generating or just a feed back
It's the base bias resistor for the transistor, it also provides a degree of both AC and DC negative feedback - this allows you not to have to select the resistor value for the particular specimen of transistor you use. However, it does reduce the gain of the amplifier, due to the AC feedback.
The purpose of the feedback resistor is not "lowering the noise frequency band". The purpose is to provide base bias current.electronic mind said:So the feedback resistor is for narrowing the noise frequency band!!!
u sadi that the simulation gave that the frequency is 16KHz ,,,,
how could u get this specific frequency although there is no kind of filters or frequency selectors??
another thing..... this Transistor is for amplifying the nosie ,,,, in my ciruit after the the transistor there is an Op Amp. .... then could it be that this transistor has another job beside the amplification??
Here is a **broken link removed**, which is supposed to be useful for audio testing. I uses a zener (reverse-biased base-emitter junction) as the noise source. A Google search for "pink noise generator" and "white noise generator" will get you lots of hits.Dr.EM said:Could someone create a schematic of how this would be used to generate audio noise? That would be really useful! Would it be white noise?
Dr.EM said:Could someone create a schematic of how this would be used to generate audio noise? That would be really useful! Would it be white noise?
Dr.EM said:Ah. White noise is fine. I found this:
**broken link removed**
I assume then that the pink noise section is only a filter for the white noise?