Nippon Telegraph and Telephone Corporation

Yukio Akazawa

Makoto Nakamura

Noboru Ishihara

Tsutomu Wakimoto

Masayuki Ishikawa

An amplifier having an automatic threshold control circuit (ATC) and a limiting amplifier. The ATC detects and holds a top value (peak value) and bottom value of an input signal, and outputs the middle value between the top and bottom values as a reference voltage. The limiting amplifier amplifies the input signal in a linear operating region whose center is set at the reference voltage, thereby maintaining the output amplitude at a constant value. Even if the amplitude and the level of the input signals instantaneously changes by a large amount, the ATC can follow the change, so that the offset compensation and gain compensation of the amplifier can be achieved instantaneously. This makes it possible to continue producing the output of a constant amplitude with little phase deviations.

Amplifier for stably maintaining a constant output

Wideband amplifier having a differential amplifier or single-ended amplifier and having a capacitaqnce compensation circuit is disclosed. The amplifier detects the voltage variations of a signal input node or a signal output node, generates a compensation current equal in magnitude and opposite in direction to a current flowing in a parasitic capacitance such as a transistor junction capacitance, and cancels the parasitic capacitance associated with a node by supplying the compensation current in a reverse phase to the node to which the parasitic capacitance is attached. As a result, a wideband amplifier is achieved, and it can also be used as a high-speed comparator. Further, harmonic distortions causing from the voltage dependency of the parasitic capacitance can be reduced by flowing the compensation current corresponding to a voltage impressed to the junction capacitance.

Growing community of inventors

Isehara, Japan

Yukio Akazawa