National Semiconductor Corporation

Linear Technology Corporation

Elantec, Inc.

John W Wright

Robert C Dobkin

William H Gross

Dennis M Monticelli

A method and circuit for increasing the output impedance of an inactive amplifier is provided. The method and circuit allows an increased number of amplifiers to be coupled in parallel to a single transmission line for distributing a plurality of video or other electrical signals to a remote location. The method and circuit increasing the impedance of an amplifier feedback network during inactive operation using a bootstrapping technique (i.e., by driving the feedback network) so as to increase the overall impedance of the amplifier during such operation.

Method and circuit for increasing the output impedance of an inactive

A new level shifting circuit is presented which does not restrict the upper limit of the common-mode input range of an operational amplifier. This is important particularly in operational amplifiers designated to operate with low power supply voltages. Significant parameters. of the operational amplifier, such as the gain and the slew rate, can be controlled without adversely affecting the common-mode input voltage range. The level shifting stage operates nondifferentially to avoid stability problems found in differential stages. A further improvement is accomplished using current balancing to achieve gain enhancement.

Level shift circuit with gain enhancement

A reference voltage generator is presented for use in a differential amplifier. The reference voltage provided by the generator tracks the non-signal dc conditions of a differential input stage and provides a reference voltage to a level-shifting stage so that feedforward compensation can be used to provide extended bandwidth without settling time problems.

Precise reference voltage generator for feedforward compensated

An improved linear amplifier circuit includes controlled current sources connected to supply additional current to the output stage during rapid change of applied signal. The current sources are responsive to current levels in the input stages and thus need only conduct low levels of current during quiescent operating conditions. Symmetrical and asymmetrical circuit configurations with respect to reference potential are disclosed.

High slew rate linear amplifier

An improved linear amplifier circuit includes current mirror circuits that are cross connected in the collector circuits of input transistors for supplying proportional current to circuit nodes from which signal is derived for controlling the output stages. The states for supplying boost current to the circuit nodes are stabilized in quiescent condition to avoid delays commonly associated with the turning on of a non-conducting stage.

Linear amplifier with transient current boost

A high speed buffer circuit is composed of complementary symmetry emitter follower driver and output stages. The input of driver stage includes active load devices cross-coupled to the output stage inputs so that the output stage is bootstrap driven from emitter followers. The circuit is biased by level shifting means to operate as a class AB current amplifier. It displays a wide bandwidth along with a high slew rate and can source or sink a large pulsed current.

High speed current amplifier buffer circuit

A unity gain amplifier circuit has a control characteristic which permits a variation of the high frequency roll off as a function of a control voltage. Means are provided to prevent a change of output voltage resulting from the control voltage variation.

Wide dynamic range control amplifier with offset correction

An audio power amplifier is designed to have a wide band high fidelity response suitable for FM radio performance. The amplifier rolloff of gain versus frequency is made sufficiently steep to reduce the gain to a negligible level at the standard AM broadcast band. A stabilization network is incorporated into the amplifier to avoid instabilities that might result in oscillation. The amplifier has a very low AM broadcast band radiation so that it is useful in AM-FM radio receivers.

Growing community of inventors

Los Altos, CA, United States of America

John W Wright