Fast Amplifier Circuit with DC Stabilization

This amplifier circuit combines the LT1010 and a fast discrete stage with an LT1008 based dc stabilizing loop. A differential stage which is single-ends into the LT1010 is formed by Q1 and Q2.  An output of 1 V pk-pk into a typical 75-Ω video load is delivered by the circuit.  With gain = 2, the gain is  considered flat  up to 10MHz  since it only  attenuated about -0.5dB, with the -3 dB point occurring at 16 MHz.  At gain = 10, this amplifier flat curve will be up to 4 MHz (0.5dB deviation), with -3 dB point at 8 MHz.  The peaking adjustment should be optimized under loaded output conditions. This is a simple stage amplifier for fast applications where relatively low output swing is required. For video amplifier application, 1 V pk-pk output works nicely. A possible problem is the relatively high bias current, typically 10 μA. Additional swing is possible, but more circuitry is needed.

[Circuit’s schematic diagram source: seekic.com]