Direct-coupled amplifier

A direct-coupled amplifier or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. A direct-coupled amplifier or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. The common use of the term 'DC amplifier' does not mean 'direct current amplifier', as this type can be used for both direct current and alternating current signals. The frequency response of the direct coupled amplifier is similar to low pass filter and hence it is also known as 'Low-Pass Amplifier'. The amplification of DC (zero frequency) is possible only by this amplifier, hence it later becomes the building block for differential amplifier and operational amplifier. Furthermore, monolithic integrated circuit technology does not allow the fabrication of large coupling capacitors.