Here's a simple emitter follower:
Version 4 SHEET 1 880 680 WIRE 272 -112 224 -112 WIRE 368 -112 272 -112 WIRE 368 -64 368 -112 WIRE 368 64 368 16 WIRE 224 96 224 -112 WIRE -32 144 -112 144 WIRE 112 144 48 144 WIRE 128 144 112 144 WIRE 160 144 128 144 WIRE 464 176 400 176 WIRE 528 176 464 176 WIRE -112 208 -112 144 WIRE 400 224 400 176 WIRE 128 240 128 144 WIRE 352 240 128 240 WIRE 224 288 224 192 WIRE 272 288 224 288 WIRE 352 288 272 288 WIRE -112 336 -112 288 WIRE 224 336 224 288 WIRE 400 352 400 304 WIRE 224 480 224 416 FLAG 224 480 0 FLAG 368 64 0 FLAG -112 336 0 FLAG 400 352 0 FLAG 464 176 ERR FLAG 272 -112 C FLAG 112 144 B FLAG 272 288 E SYMBOL npn 160 96 R0 WINDOW 0 95 31 Left 2 WINDOW 3 73 62 Left 2 SYMATTR InstName Q1 SYMATTR Value 2N4401 SYMBOL current 224 336 R0 SYMATTR InstName I1 SYMATTR Value 10m SYMBOL voltage 368 -80 R0 SYMATTR InstName V1 SYMATTR Value 10 SYMBOL voltage -112 192 R0 WINDOW 0 48 57 Left 2 WINDOW 3 41 96 Left 2 WINDOW 123 43 129 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value SINE(0 0.5 1) SYMATTR Value2 AC 1 SYMBOL res 64 128 R90 WINDOW 0 -60 55 VBottom 2 WINDOW 3 -49 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 1m SYMBOL e 400 208 R0 WINDOW 0 51 53 Left 2 WINDOW 3 56 87 Left 2 SYMATTR InstName E1 SYMATTR Value 1 TEXT -32 -16 Left 2 !.tran 10 TEXT -96 -104 Left 2 ;Emitter Follower Gain TEXT -64 -64 Left 2 ;JL April 4, 2015
Spice reports the error as 270 uV p-p (ie, 270 PPM, gain = 0.99973). The base input impedance looks like about 2.2 megs. Is that gain realistic?
The LT Spice 2N4401 model has the forward Early voltage Vaf=90.7, and no reverse Early voltage, whatever that is. The 90 volts is actually kinda low; some NPNs are over 1000.
AoE3 reports the measured 2N4401 Ve as 410.
This gain would be a mild nuisance to measure.