Abstract: Method and apparatus for generating a distortion-free, frequency-modulated optical signal, whereby this signal from an optical semiconductor laser driven with a modulating voltage is distorted by the modulating voltage due to a thermally conditioned frequency transfer function of the transmitter for the modulation frequency of the modulating voltage. For generating the distortion-free, frequency-modulated optical signal, the modulating voltage and/or the distorted, frequency-modulated optical signal itself and/or a superimposition signal containing this optical signal is subjected to a distortion that entirely or partially compensates the distortion of this optical signal. This method is simple and, in combination with receivers for the frequency-modulated optical signal, avoids sensitivity losses.

Abstract: 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.

Abstract: The invention includes a simple and inexpensive thermal controller and simple and inexpensive radio frequency alternating current generator which are provided in an improved temperature control system for a resistively heated electrochemical cell. The temperature controller is formed by a single amplifier with feedback circuit which provides the function of a combined deviation amplifier and two mode (percent proportional band and integral functions) controller. The alternating current generator uses a single direct current voltage source to generate a radio frequency alternating electric current. The two elements are combined in a temperature control circuit for a resistively heated electrochemical cell. The control circuit provides an alternating current with varying power by cyclicly shutting the current off for irregular portions of a predetermined cycle period.

Abstract: A voltage-to-current converter circuit for outputting a current accurately proportional to the input signal voltage, which converter circuit includes an operational amplifier for providing an output corresponding to a difference between the input signal and a feedback signal, and includes a feedback circuit for detecting the output current in the form of a voltage by making the output current flow through the reference resistor and for feeding back the detected voltage. Further, the feedback circuit includes a polarity inverting circuit which holds the voltage detected by the reference resistor and inverts the polarity of the voltage, and then feeds back to the operational amplifier.

Abstract: A d.c. high voltage operational amplifier. The output of a conventional power operational amplifier is converted to a.c. which is stepped up by a transformer and then rectified to provide a high voltage d.c. output. Appropriate feedback circuitry is utilized to stabilize the overall operational amplifier against oscillation and provide substantially perfect linearity between the input and output voltages of the high voltage operational amplifier when incorporating negative feedback.

Abstract: A low distortion amplifier arrangement includes an amplifier having an inverting input, a non-inverting input, and an output, a first impedance coupled between the output and the inverting input, and a second impedance coupled between an input terminal of the amplifier arrangement and the amplifier inverting input. An impedance network is coupled between the inverting and the non-inverting inputs of the amplifier. The impedance value of said impedance network substantially corresponds to the impedance value of the parallel connection of the first impedance and the second impedance, but with opposite sign. The gain of the amplifier arrangement is independent of the gain of the amplifier and corresponds to the ratio of the impedance values of said first and second impedances to produce an amplifier arrangement with a very low distortion.

Abstract: A signal isolator including a coupling transformer with modulate/demodulate switches in series with the primary and secondary windings. The switches are driven in synchronism by an oscillator. Resonating capacitors are connected in parallel with the transformer windings and tuned to the switch operating frequency to control the flux in the transformer core. A transformer turns-ratio of less than unity introduces a corresponding attenuation, and a following amplifier counteracts that attenuation to produce an output signal at the original level. A return current resistor is connected between the output signal and the transformer secondary to produce a back-flow of current towards the transformer. This current provides for supplying the losses of the coupling circuit in a symmetrical fashion, both from the isolator input and its output, to reduce significantly variations in performance resulting from changes in ambient temperature.

Abstract: A transformer-coupled isolation amplifier which has a minimally sized transformer, high common mode rejection, and a highly linear response over a wide dynamic range. A first chopper periodically alternates by 180.degree. the connection of the input through a high resistance to the primary of a small square loop pulse transformer. The secondary, with the end of the winding closest to the primary grounded, has the inputs of an operational amplifier placed across it. Negative feedback is provided around the amplifier to provide an apparent very low impedance across the secondary of the transformer. The negative feedback induces a current in the transformer secondary which cancels the flux produced by current flowing in the primary, thereby allowing usage of the transformer normally suitable only for high speed pulses. The output of the amplifier connects to a second chopper synchronous with the first to generate the amplified analog signal.

Abstract: A transformer-coupled isolation amplifier which can accept signals over a wide dynamic range while maintaining very high linearity. An input signal is applied to an input winding of a transformer. The secondary winding of the isolation transformer is connected across the differential inputs of a high-gain amplifier. Negative feedback is provided around the amplifier so that the transformer secondary winding is connected across a virtual short; and the negative feedback tends to drive the voltage applied to the inputs of the amplifier to a very small value. The negative feedback from the amplifier induces a current in the transformer secondary which cancels the flux produced by current flowing in the primary, thereby reducing the effects of non-linearities in the BH curve of the transformer.

Abstract: A direct coupled linear amplifier which employs negative feedback to prov accurate and stable gain to AC as well as DC input signals. It also performs the function of a DC level shifter and can therefore be interfaced with a variety of signal sources. A constant current source added to the summing junction of the negative feedback amplifier enables the adjustment of the DC level of the output and the AC gain of the amplifier, completely independently of one another.

Abstract: A pulse width modulation circuit which comprises a mixer for combining an input audio signal with a feedback signal and for developing a difference signal to feed to an integration circuit. The integration circuit is coupled to a pulse width modulator which has a sawtooth carrier input for modulating the input audio signal. The resulting pulse modulated signal is then fed to a pulse amplifier and a low-pass filter and finally to a load. The output of the low-pass filter is coupled back to the mixer.

Abstract: A pulse width modulated signal amplifier includes a first input terminal supplied with a rectangular wave signal as a carrier, a second input terminal supplied with a modulating signal, such as an audio signal, an integrator supplied with both the rectangular wave signal and the modulating signal, a high gain amplifier receiving the output of the integrator, a low pass filter receiving the output of the high gain amplifier and producing a demodulated signal corresponding to the modulating signal and which is supplied to an output terminal, and a negative feedback circuit connected between the output of the high gain amplifier and the input of the integrator.

Abstract: A pulse width modulated signal amplifier system includes a signal input circuit, an amplifier for receiving an input signal from the signal input circuit, a pulse width modulator for receiving an output signal from the amplifier and producing a pulse width modulated signal, and a phase splitter for receiving the pulse width modulated signal and producing a pair of corresponding pulse width modulated signals having different polarities to each other.