Atmel Germany Gmbh

Juergen Eckert

Juergen Schnabel

Hans-Peter Waible

Wolfgang Roeper

Horst Haefner

Reinhard Reimann

Burkhard Gehring

Thorsten Fahlbusch

Friedemann Schmidt

Gerald Krimmer

Hermann Hammel

Hans-Werner Groh

Michael Hecker

Wolfgang Schneider

Michael Vogt

A d.c. signal controlled oscillator includes a frequency-determining network having a control input and a modulation input. A phase regulating loop includes the oscillator and components that provide a control signal to the control input. A circuit apparatus for driving the oscillator includes a modulation generator that provides a modulation signal to the modulation input, and a circuit arrangement that autonomously generates a signal depending on and representing a slope of the modulation and provides this slope signal to the modulation generator, which generates the modulation signal dependent on the slope signal. A method of operating the oscillator involves switching a frequency divider successively to two different frequencies, respectively sampling and holding the two different arising control voltages, forming a difference between the two control voltages, and activating the modulation generator so that a modulation swing of the modulation signal is determined by this difference between the control voltages.

Method and apparatus for driving a direct current or voltage controlled oscillator with modulation slope feedback

A control unit and two negative feedback branches limit the amplitudes of the output signal of an inverting differential amplifier. Each feedback branch includes a threshold value switch including a transistor as well as an adjustable current source and a resistor forming a voltage divider between a supply voltage and the amplifier output. The voltage divider output is connected to the transistor's base. The transistor selectively connects or disconnects the input of the amplifier with either the supply voltage or the amplifier output. The control unit controls the two current sources based on external programming commands, to establish two adjustable threshold values within which the negative and positive amplitudes of the output signal are limited, symmetrically or independently, in a hard or soft clipping manner. Even with small supply voltages, the limited output will not overdrive subsequent amplifier input stages and will not superimpose harmonics on the useful signal.

Amplitude limiting method for a differential amplifier

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Neckarsulm, Germany

Juergen Eckert