feedback on my design

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I thought that Q1 was kindof strange... no idea why I never tried to correct it. My problem with the simulator is that all the circuits I make usually work! Are there any better free simulators than LTSpice/SCADIII? This one doesn't get the transistors right... it is mainly for building switching power supplies so the transistors are switching-quality simulation (pardon my grammatical errors). I know that transistors are supposed to be biased at around .6V, this is why the 4QD circuit threw me off about the double diode biasing thing. Do you have to bias transistors with current too? From what I know, BJT's mainly react to current which I suppose would mean that you want the least current flowing through them at no input but the right amount of voltage bias. I have seen a hypothetical voltage-current transistor curve, and I think I know about biasing, but obviously there are some things I don't know about. Please help... :bawling:
 
LTSpice is a wonderful simulator, with high quality models (I believe it uses the Gummel-Poon model, a very accurate modeling method) quite suitable for linear circuit simulation.

You're going about biasing the wrong way, biasing must be tolerant of wide component variation. Look at the standard NPN emitter follower circuit, the input (the base of the transistor) is held near ground, the collector is connected to a positive voltage, and a resistor connects the emitter to ground. The emitter voltage follows the base voltage (hence the name) so with the base grounded the negative supply voltage appears across the resistor, I=V/R, so a well defined current flows through the transistor regardless of what type or model of transistor it is. There is no finnicky ajusting of variable resistors and there are no capacitors, those things arn't needed for stable biasing.
 
ok, just for the sake of optimization, which integration method is better-Trapozoidal, Modified Trap (I have this one on), or Gear?.
Also, which DC solve is better-Noopiter, or [Skip Gmin Stepping], I have none of these checked. I always thought that the base had to be positive potential on NPN transistors! (is this what you mean by "near Ground"? I have a feeling I might be wrong... Again... :rolleyes: ) No wonder!
 
The base has to be held at a positive potential relative to the emitter. For an emitter follower the base has to be held one Vbe above ground for the output to be at ground (that's what I meant by near), if you bias that base at ground the circuit will still work just with about 0.7v of DC offset.

No matter what the circuit, if an NPN transistor is operating in it's linear range, the emitter will follow one Vbe below the base (one Vbe below for PNP).
 
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