I'm looking at the phase splitter design, discussed briefly in the Art of Electronics, Fig 2.27 (in an old edition, later chapters in the new one):
(
I'm rather puzzled by the LTspice results from the DC transfer function (with coupling cap shorted, and DC offset set to operating Vb):
--- Transfer Function ---
Transfer_function: 0.993969 transfer v2#Input_impedance: 39651.7 impedance output_impedance_at_V(out0): 27.2453 impedance
Rin seems about right. But Rout0 & Rout180 seem way off.
Isn't Zout (at emitter) = Zsource / ( Beta + 1 ) ?
But if I put a 50 ohm Rs in the circuit where the short circuit is shown (and unhook C1), the Rout0 only increases very slightly from 27.5 ohms. With this calculation, Zsource would have to be about 8.3k to arrive at
27 ohms, since Beta=300. Or is Zsource something else here?The other puzzling thing is why is Rout180 reading about 5.6k ohms? With R1=4.7k ohms, I have trouble with that answer.
LTspice file below. Thanks, Warren
............................................. Version 4 SHEET 1 880 680 WIRE 208 -112 32 -112 WIRE 528 -112 208 -112 WIRE 32 -80 32 -112 WIRE 208 -80 208 -112 WIRE 528 -80 528 -112 WIRE 32 16 32 0 WIRE 32 16 -128 16 WIRE 208 32 208 0 WIRE 272 32 208 32 WIRE 352 32 272 32 WIRE 208 48 208 32 WIRE -288 96 -304 96 WIRE -128 96 -128 16 WIRE -128 96 -288 96 WIRE -80 96 -128 96 WIRE 32 96 32 16 WIRE 32 96 -16 96 WIRE 96 96 32 96 WIRE 144 96 96 96 WIRE -288 176 -288 96 WIRE 208 176 208 144 WIRE 272 176 208 176 WIRE 352 176 272 176 WIRE 32 192 32 96 WIRE 208 192 208 176 WIRE -288 304 -288 256 WIRE 32 304 32 272 WIRE 32 304 -288 304 WIRE 208 304 208 272 WIRE 208 304 32 304 WIRE 528 304 528 0 WIRE 528 304 208 304 WIRE 208 336 208 304 FLAG 208 336 0 FLAG -304 96 In IOPIN -304 96 In FLAG 352 32 Out180 IOPIN 352 32 Out FLAG 352 176 Out0 IOPIN 352 176 Out DATAFLAG 96 96 "" DATAFLAG 272 32 "" DATAFLAG 272 176 "" SYMBOL Misc\\battery 528 -96 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 20V SYMBOL npn 144 48 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 192 -96 R0 SYMATTR InstName R1 SYMATTR Value 4.7k SYMBOL res 192 176 R0 SYMATTR InstName R2 SYMATTR Value 4.7k SYMBOL res 16 -96 R0 SYMATTR InstName R3 SYMATTR Value 150k SYMBOL res 16 176 R0 SYMATTR InstName R4 SYMATTR Value 56k SYMBOL cap -80 112 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName C1 SYMATTR Value 4.7uF SYMBOL voltage -288 160 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 132 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(5.3134 .5 60Hz) TEXT -288 360 Left 0 !;tran 0 .2 0 .001 TEXT 344 0 Left 0 ;5597ohms TEXT 352 144 Left 0 ;27.5ohms TEXT -88 360 Left 0 !.tf V(Out0) V2 TEXT -296 -8 Left 0 ;Shorted for Transfer\nFunction only..