Motorola Corporation

Michael W Null

Robert N Dotson

Ira G Miller

Robert Bruce Davies

Paul M Erickson

Charles W Bethards

William Arthur Burzynski

Susumu Cho

Robert B Davis

In a circuit for converting signals having ECL logic levels to a signal having TTL logic levels, the level shift is accomplished using the base-emitter drops of the transistors employed to avoid the speed degradation that accompanies the use of resistors as level shifters. First and second complementary input ECL signals are applied to first and second transistors respectively. The first input signal results in rendering a drive transistor conductive which turns the source transistor means in a push-pull output stage off and the sink transistor in the output stage on. When the second input signal goes high, current is diverted so as to render the drive transistor nonconductive. Additional circuit means are provided for preventing the sink transistor from saturating and for preventing the input of the source transistor means from falling below a predetermined level. Circuit means are also provided for turning the source transistor means off quickly so as to improve the overall speed performance of the circuit.

ECL To TTL output stage

A current amplifier is provided having a single control amplifier and a plurality of output stages. The desired output stage is digitally selected. The ratios of the output stage currents may be selected during the metalization process. A single capacitor compensates for all output stages regardless of which output stage is selected.

Current amplifier having multiple selectable outputs

A pulse stretching integrated circuit includes an on-chip capacitor. A first transistor means including an input transistor and an emitter follower transistor supplies a charging current to the capacitor so as to charge it to a first voltage when an input signal pulse is in a first logical state. A differential transistor pair has a first input coupled to the emitter follower transistor and to the capacitor and has a second input coupled to a reference voltage for generating a first output when the capacitor voltage is less than the reference voltage and for generating a second output when the capacitive voltage is greater than the reference voltage. An additional transistor is coupled to the capacitor for discharging the capacitor when the input signal pulse is in a second logical state causing the voltage at the first input of the differential pair to fall below the reference voltage.

Pulse stretching and level shifting circuit

A current amplifier uses a current mirror arrangement as an operational amplifier whose output has limited swing. The limited swing is achieved through a plurality of series connected diodes connected to a control input of the amplifier and to the output of the operational amplifier. The control input is coupled through a transistor to inhibit the output of the current mirror arrangement. The output node is coupled to an output for the current amplifier through a Darlington arrangement which provides high current gain.

Current amplifier

An electronic pushbutton tunable radio (10) having various audio controls is disclosed. A single pushbutton (22) is utilized to implement volume, fader and balance modes of operation during which up/down pushbuttons (20,21) control the overall and relative magnitude of audio signals produced by four speakers (24-27) while at the same time a single display (17) is utilized to display, respectively, either the channel to which the radio is tuned, the relative magnitude between right and left speaker audio signals, or the relative magnitude between front and back speaker audio signals. The radio has tuning pushbuttons (14) for direct recall of preset radio channels in a tuning mode operation. The radio includes an audio mode pushbutton (23) which terminates the tuning mode and implements an audio control mode wherein the recall tuning pushbuttons (14) now serve as on/off manual controls for audio control circuits, such as the radio local/distant (L/D) circuit, while at the same time utilizing the display (17) previously utilized to indicate channel frequency to now indicate the operative state of the audio circuits controlled by the recall pushbuttons in the audio mode.

Radio with audio controls and associated displays

An audio signal quality detector connected to receive an audio signal from the discriminator of a radio receiver and including an envelope detector connected to the output of the discriminator and supplying a signal indicative of the envelope of the audio to a resettable valley detector which stores a voltage indicative of the lowest valley applied thereto subsequent to a reset pulse and a sample and hold gate connected to the valley detector for sampling the voltage stored in the valley detector prior to periodic reset pulses applied to the valley detector. Circuitry is also included for inhibiting the operation of the sample and hold gate when there is no output from the valley detector.

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Mesa, AZ, United States of America

Michael W Null