mstechca said:The yellow circuits are the "miller effect" circuits.
He mentioned a resistor and capacitor in series, then proceeded to highlight some parallel RC networks. I'll have some of whatever you're having, Mstechca.Nigel Goodwin said:mstechca said:The yellow circuits are the "miller effect" circuits.
Perhaps you read about 'miller effect' somewhere, and liked the sound of it?.
Those components aren't anything to do with 'miller effect', they are simply bypass capacitors for the emitter resistors - bypassing them in that way increases the gain, by reducing the negative feedback around the transistor. All altering the value of the capacitor will do is alter the amount of bass, reducing it as the capacitor gets smaller.
That's weird, because when I tested it, I didn't notice an increase in volume. The circuit I explained above produced a clear audio signal, but at a ridiculously low volume.Nigel Goodwin said:The yellow increases the gain, by reducing the negative feedback around the transistor. All altering the value of the capacitor will do is alter the amount of bass, reducing it as the capacitor gets smaller.
He mentioned a resistor and capacitor in series, then proceeded to highlight some parallel RC networks. I'll have some of whatever you're having, Mstechca.
Russlk said:I assume this is a superregen receiver, where is the antenna?
It is not a final circuit.Russlk said:That is a wierd circuit!
I can connect an antenna to the Pn3563's emitter. or I can connect the antenna to +ve, which provides somewhat better reception.Is there an input somewhere?
The 2n3904, and the capacitor connected to it make a poor-man's varactor I'm using 2 of them and connecting their inputs to the same source through resistors, so that I can gang-tune my circuit without the need of two separate trim capacitors.What are those diode-connected 2n3904 doing?
I forgot to include it in the circuit, but I can still pick up the TV station without an antenna!I assume this is a superregen receiver, where is the antenna?
A super-regen is an AM radio. TV sound is FM. FM is very distorted on an AM radio, even when you tune to the side of the FM carrier and "slope-detect" the FM. The slopes of your tuned circuit are nowhere near linear so of course the sound is distorted!mstechca said:The point is that I want to reduce distortion and obtain maximum volume
Of course. 470k is much too high for an emitter resistor. The transistor would be practically cutoff, and its voltage gain would be vey low.mstechca said:Now my base voltage happens to be substantially high, because the lowest value used for a pull-down resistor is 470K.
How is the base going to be strained???The collector resistor is 18K.
If the collector current and the emitter current are supposed to be equal, and my thinking is correct, then the emitter resistor must be close to the collector resistor, or I strain the base by adding a pull-down resistor that is lower than 82K, and if I do that, wouldn't my gain be cut greatly?
I have experimented with the resistor. (from base to ground), and it seems that a value too low will considerably reduce the range of the receiver, which means I can't pick up signals from distant transmitters.audioguru said:Of course. 470k is much too high for an emitter resistor. The transistor would be practically cutoff, and its voltage gain would be very low.
The collector resistor is 18K.
If the collector current and the emitter current are supposed to be equal, and my thinking is correct, then the emitter resistor must be close to the collector resistor, or I strain the base by adding a pull-down resistor that is lower than 82K, and if I do that, wouldn't my gain be cut greatly?
How is the base going to be strained???
What is "a pull-down resistor"???
The voltage gain of a common-emitter transistor stage that has a high resistance load is roughly the collector resistor's value divided by the emitter resistor's value. The emitter resistor can be removed or bypassed with a capacitor for much more gain...
Your emitter resistors are 4.7k but your bypass capacitors across them have a value of only 0.33uF.mstechca said:it seems better to add a resistor and a by-pass cap at the emitter instead of a short. I find the quality is better, but I seem to have a problem with volume.
This I understand.At low audio frequencies the gain of each stage is only 18k/4.7k= 3.8.
Where did you get 1.414 from?At 103Hz the gain of each stage is 3.8 x 1.414= 5.4.
I don't get what equation you are using here.At about 2060Hz and higher the gain of each stage will be about 100.
All altering the value of the capacitor will do is alter the amount of bass, reducing it as the capacitor gets smaller.
Whether I do or do not get bass, that isn't the concern.No bass whatsoever.
I plan to do that.Increase the value of the bypass capacitors to about 22uF for flat response down to 47Hz.
I don't think you will ever understand how a transistor amplifier stage works without seeing the results on an oscilloscope.
1.414 is the root of 2. At 103Hz, the capacitive reactance equals the emitter resistor's value so the gain is increased 3dB which is times 1.414.mstechca said:"At 103Hz the gain of each stage is 3.8 x 1.414= 5.4."
Where did you get 1.414 from?
A single RC network at the emitter boosts the gain two times for each doubling of frequency or boosts the gain 10 times for each 10 times the frequency. Therefore at 1030Hz (10 times the frequency that has a gain increase of 1.414) the gain would be 54. Doubling this frequency to 2060Hz then the gain would be 108 but it is max which is about 100 for a single simple transistor stage."At about 2060Hz and higher the gain of each stage will be about 100."
I don't get what equation you are using here.
You said the volume was too low. Most of the volume of sound is in the bass frequencies. A tweeter speaker that is playing by itself isn't very loud."No bass whatsoever."
Whether I do or do not get bass, that isn't the concern.
I'm real lost :?A single RC network at the emitter boosts the gain two times for each doubling of frequency or boosts the gain 10 times for each 10 times the frequency. Therefore at 1030Hz (10 times the frequency that has a gain increase of 1.414) the gain would be 54. Doubling this frequency to 2060Hz then the gain would be 108 but it is max which is about 100 for a single simple transistor stage.
mstechca said:I'm real lost :?A single RC network at the emitter boosts the gain two times for each doubling of frequency or boosts the gain 10 times for each 10 times the frequency. Therefore at 1030Hz (10 times the frequency that has a gain increase of 1.414) the gain would be 54. Doubling this frequency to 2060Hz then the gain would be 108 but it is max which is about 100 for a single simple transistor stage.
Let's say that my RC network has a 1K resistor, and a 1 uF capacitor, and the frequency being received is 200Mhz.
How do I calculate the gain according to your math?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?