Use of thermal feedback to produce 20 cps. low frequency rolloff in a microelectronic video amplifier

The low-frequency response attainable in semiconductor network ac amplifiers is limited by the large physical size required for coupling components. Better low-frequency response can be achieved with field effect amplifiers than with transistor amplifiers, but at the expense of reduced bandwidth. Hence, direct-coupled transistor stages are commonly used in semiconductor network video amplifiers when high cutoff frequencies are required. A direct-coupled video amplifier has the disadvantage, however, that a dc component will be produced in the output for either a dc input component or drift within the direct-coupled amplifier.