Plot VIN, VOUT, ENV, CTRL and I(BITAIL). The input amplitude steps from 20 mVpk to 100 mVpk at 6 ms. The detector then raises ENV; BCTRL reduces CTRL; the behavioural tail source reduces ITAIL; gm falls; and differential gain falls. This is a complete AGC signal path built around a real BJT differential pair. The behavioural detector/controller is used so the gain-cell physics remains visible. Check that the tail current always stays inside 0.05-2 mA and that neither collector clips at the rails.
