Abstract: Amplifier apparatus for precisely controlling current through an inductive load by means of an RC network which produces a feedback signal accurately simulating the load current. The RC network includes a resistor and a capacitor connected in series across the load and having values related to the parameters of the load such that a signal representative of the instantaneous load current is produced between the resistor and capacitor. The RC network may also include a T resistor arrangement to compensate for any lag occurring between the input and output signals of the amplifier.

Abstract: An amplifier comprising a series of field effect transistors is connected to a dynamic high impedance load. The output of the amplifier preferably is taken from the last stage of that load. The dynamic high impedance load may be a constant current source consisting of at least three field effect transistors.

Abstract: The bridge amplifier includes NPN transistors for performing all critical amplifying functions, diodes for providing quiescent bias and resistors which have non-critical values. Hence, the bridge amplifier is suitable for manufacture in monolithic form. In response to portions of the input signal of one polarity, a switch circuit of the bridge amplifier applies a given power supply potential to a first terminal of the electrical load and an analog stage connected to the second terminal of the load controls the magnitude of the current flowing through the load to another power supply potential. In response to portions of the input signal of the other polarity, a further switch circuit applies the given power supply potential to the second terminal of the load and a further analog stage controls the magnitude of the load current. Thus, the load current flows in opposite directions through the load under the control of portions of the input signal having different polarities.

Abstract: A load resistance change alarm in which the magnitude and frequency of an audio signal are increased in proportion to an increase or decrease in resistance of the load. The load is connected in one branch of a bridge circuit. Any imbalance across the bridge circuit caused by a change in the load resistance is applied to an amplifier having a feedback circuit. The oscillations of the amplifier circuit turn on an electronic switch which allows unilateral current flow through the speaker. The current applied to the speaker is supplied through a step down transformer from the same power supply supplying current to the load.

Abstract: A control system for controlling the supply of current to a load. The current to the load, which may comprise elements of an ionographic imaging system is sensed and when the peak thereof is reached, a level detector circuit initiates the operation of control circuits which control the supply of current to the load. The load current is maintained substantially constant by means of a power supply control which controls the output voltage of a programmable power supply during a predetermined period of time as measured by an integrator, which integrates a signal in accordance with the load current. The integrator operates to automatically cut off the supply of current to the load when the desired flow to the load has been attained.

Abstract: A signal interpreting circuit for switching an output load in response to an increasing input frequency, the circuit having a frequency to direct current converter for providing a direct current voltage varying inversely with input frequency, a load controlling circuit for continuously energizing the load as long as the direct current voltage remains the same or increases, and a capacitor-transistor circuit responsive to a decreasing of the direct current voltage for interrupting the continuously energized load.