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Why im getting shifted phase in the output voltage in this differential amplifier? and how can I eliminate this shifted phase? enter image description here

Second question is, I need to make a gain of 50 in the amplifier below, I got and Re of 1ohm is it ok? or there is other way to make this gain with higher resistor? Cause I dont sure that 1ohm resistor is legit...

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  • \$\begingroup\$ The phase shift is mainly due to RL*C7 compared to 1/f. You must not have R32<R7 for full swing as it current starves the collector.. \$\endgroup\$ – Sunnyskyguy EE75 Dec 29 '18 at 17:37
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    \$\begingroup\$ How did you arrive at 1 ohm for Re? \$\endgroup\$ – Chu Dec 29 '18 at 17:44
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You have 200 milliAmps of Tail current in the differential amplifier. The base currents cause large voltage drops across R30 and R31.

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Q1. Increase RL, C7 or the frequency to reduce phase difference.

Tail current is 23V/250R = 90mA which is 45mA per side approx. Assume B=200 which gives Ib of 0.225mA. Quiescent voltage across base bias resistors is 0.225mA * 10K = 2.25V. To reduce base bias resistor volts drop, reduce base resistors value but this will increase the -3dB frequency and the phase diff unless you proportionately increase C12 & C13.

Q2. Increase R9 to 10K Replace R16 with two resistors 200R connected to ground and 33R connected to emitter. Increase R32 to 10K. The smaller R32 is, the more the gain is reduced. Connect 100uF cap across 200R resistor.

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