Hi,
I'm new to Fuzz design but I've been doing a lot of reading lately and a couple of days ago I came across the idea of connecting Silicon transistors in parallel in order to reduce gain (often needed as silicon trannies are way hotter than the germanium ones).
I've bought a PEAK atlas DCA55 component analyzer that takes readings of HFE (+ many other things) but when I solder two transistors together I still get half the same HFE measurement instead of half the gain, which was what I expected...
I've also heard about simulating the leakage - from collector to base - in GE trannies by connecting a large resistor from collector to base on a silicon transistor but when doing so I don't get an reading of leakage as it remains at "Zero".
Something DOES happen though!
Gain now have dropped from about 330 (BC547B transistor) to 7 !?...
And what seems even stranger, collector and emitter have now "switched places" according to my component analyzer !?...
Will these things: "transistor in parallel/half the gain" and "leakage resistor" work differently IN a circuit?
Someone please explain
Transistors in parallel + simulating leakage
- DrNomis
- Old Solderhand
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polifemo wrote:Hi,
I'm new to Fuzz design but I've been doing a lot of reading lately and a couple of days ago I came across the idea of connecting Silicon transistors in parallel in order to reduce gain (often needed as silicon trannies are way hotter than the germanium ones).
I've bought a PEAK atlas DCA55 component analyzer that takes readings of HFE (+ many other things) but when I solder two transistors together I still get half the same HFE measurement instead of half the gain, which was what I expected...
I've also heard about simulating the leakage - from collector to base - in GE trannies by connecting a large resistor from collector to base on a silicon transistor but when doing so I don't get an reading of leakage as it remains at "Zero".
Something DOES happen though!
Gain now have dropped from about 330 (BC547B transistor) to 7 !?...
And what seems even stranger, collector and emitter have now "switched places" according to my component analyzer !?...
Will these things: "transistor in parallel/half the gain" and "leakage resistor" work differently IN a circuit?
Someone please explain
When you connect a large value resistor from a Silicon Transistor's Collector to it's Base, the resistor biases the transistor "on" by diverting some of the current from it's Collector to it's base...
Silicon Transistors typically exhibit leakage-currents in the order of Nano-Amps, one Nano is one one-thousandth of a Micro-Amp, Germanium Transistors typically exhibit leakage-currents in the order of Micro-Amps, so the Leakage Current is about a thousand times greater than for Silicon Transistors....
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
- polifemo
- Breadboard Brother
In my initial post the word "Half" was misplaced due to a cut n´paste procedure....
"I've bought a PEAK atlas DCA55 component analyzer that takes readings of HFE (+ many other things) but when I solder two transistors together I still get ( half) the same HFE measurement instead of half the gain, which was what I expected..."
I meant that I get THE SAME READING!
My component analyzer do not display any leakage at all when soldering a 1 meg transistor from collector to base.
Maybe I should try a really small one?
I´ll be able to test IN a circuit when some new compnents have arrived
"I've bought a PEAK atlas DCA55 component analyzer that takes readings of HFE (+ many other things) but when I solder two transistors together I still get ( half) the same HFE measurement instead of half the gain, which was what I expected..."
I meant that I get THE SAME READING!
My component analyzer do not display any leakage at all when soldering a 1 meg transistor from collector to base.
Maybe I should try a really small one?
I´ll be able to test IN a circuit when some new compnents have arrived
- DrNomis
- Old Solderhand
Information
- Posts: 6807
- Joined: 16 Jul 2009, 04:56
- my favorite amplifier: Self-Built Valve Amp Head :)
- Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
- Location: Darwin,Northern Territory Australia
- Has thanked: 98 times
- Been thanked: 278 times
polifemo wrote:In my initial post the word "Half" was misplaced due to a cut n´paste procedure....
"I've bought a PEAK atlas DCA55 component analyzer that takes readings of HFE (+ many other things) but when I solder two transistors together I still get ( half) the same HFE measurement instead of half the gain, which was what I expected..."
I meant that I get THE SAME READING!
My component analyzer do not display any leakage at all when soldering a 1 meg transistor from collector to base.
Maybe I should try a really small one?
I´ll be able to test IN a circuit when some new compnents have arrived
HFE is basically the same as a Transistor's gain, what you are actually measuring is the Transistor's "Current-Gain" (assuming it's a Bi-Polar Transistor), that is, how much larger the Collector-Current is compared to the current flowing into the Base of the transistor, say for example the HFE of the transistor is 200, if we apply a current of 1 micro-amp to the transistor's base, we would have 200 micro-amps Collector-Current, another name for a Transistor's Current-Gain that's commonly used is "Beta"....
The Collector-Current of a Bi-Polar Transistor is calculated using the following Mathematical Formula:
Note:
Ic = Collector Current.
Ib = Base Current.
B = Beta, or HFE (Current Gain).
Ic = Ib X B
Try changing the 1M resistor to a lower value resistor, say 100k, or maybe 220k....
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.