A Darlington emitter follower circuit is sometimes used in the output stage of TTL gate to _____.

Explanation:1. A Darlington pair configuration has high input impedance and low output impedance.2. Thus it is used as a buffer circuit for impedance matching with the circuits that require high input impedance at the input.3. In addition to providing high input impedance, the Darlington pair also provides high current gainHence a Darlington emitter follower circuit is sometimes used in the output stage of the TTL gate to increase speed.Note:Darlington Pair: CC – CCA Darlington pair is a two-transistor circuit with the emitter of one transistor is CONNECTED to the base of other TRANSISTORS, while both collector terminals are connected to the common terminalIt has a high current gain β; (equal to the PRODUCT of the current gain of individual transistors) and is useful in applications where current amplification or switching is required.It also has high input impedance and low output impedance.The current gain of a Darlington pair in common emitter configuration is approximate β2 The symbolic diagram of the Darlington pair is shown below