# Feedback loop gain not as expected in a differential amplifier

I am trying to build an approximate opamp with a differential amplifier and add a feedback loop to get the approximate wanted gain.

I used a differential amplifier with a current source and a current mirror, and got open loop gain of 3k.

When I add the feedback loop resistors I expect to get:

$$A_{cl} = \frac{A_OL}{1 + A_OL \beta}\cdot K =\frac{3k}{1 + 3k\cdot\frac{1}{1+20} }\cdot\frac{20}{1+20} \approx 19.8$$

Instead I get $$A_{CL} \approx 70$$

I don't understand what I'm doing wrong, and if what I want to do is even possible.

EDIT: In the schematic below I placed by mistake a feedback resistor of 50k instead of 20k like my original circuit.

I also forgot to mention, for the NPNs and PNPs: $$\beta = 100, V_A = 100[V]$$

simulate this circuit – Schematic created using CircuitLab