A Wideband Direct Coupled Amplifier Utilizing a Fast/Slow Loop Concept

A new direct coupled wideband amplifier, using thick film hybrid integrated circuit technology, has been designed and tested. A fast/slow loop configuration is used to provide a constant closed-loop voltage gain from dc to the closed-loop -3dB bandwidth of the fast stage. Analytical expressions are derived for the voltage transfer function. The risetime of the amplifier is < 2.5ns with < 10% overshoot for output signals to ± 5 volts into a 50-ohm load. The voltage gain can be varied from 2 to 10 while maintaining a constant 200MHz bandwidth. The measured dc drift was 27 μV/0C referred to the input. Three hybridized amplifiers have been included in the implementation of a fast filter amplifier.