U.S. Philips Corporation

Siemens Aktiengesellschaft

Axel Nathe

Ralf Beier

Jurgen Kordts

Marten Swart

Horst Belau

Friedrich E Hahn

Paul Sonnenberger

Michael Ramm

Peter Rolla

The binary values of the data word to be converted in a widely used type of D/A converter are supplied to a series of stages in which binarily stepped currents are supplied to a common output or derived therefrom, or are conducted to a second common output. To control the current switch, each stage comprises a flipflop in which the binary value to be converted is stored. Integration processes are often used in the integration of analog circuits by means of which digital circuit components cannot be usefully realized, for example, in the IIL technology. In the flipflop comprising cross-coupled transistors, the emitters are connected to a reference voltage which lies between ground potential and the supply voltage so as to obtain a favorable conversion of the digital signals for triggering the current switch. This renders it possible to connect the collectors of the transistors of the flipflop directly to the bases of the current switch. In addition, the control of the flipflop is simplified thereby, and the delay time is shortened.

Circuit arrangement for a memory cell of a D/A converter

A controlled power supply source is described, which has a parallel control member having a controllable semiconductor component whose load path is arranged between output terminals of the power supply source and whose control input is connected to an output of a control device, the control device having a reference input for supplying a reference voltage. The control device has a control amplifier which is fed from a current bank having at least one constant current source, an actual value input of said control amplifier receiving the voltage between the output terminals of the power supply source, and a nominal value input receiving the reference voltage from the reference input of the control device. An output of the control amplifier constitutes the output of the control device which further has a preliminary current stage which, dependent on the difference between the voltages at the actual value input and at the nominal value input of the control amplifier, applies a preliminary current to this control amplifier, which preliminary current is applied to the control input of the semiconductor component at least partly via the output of the control device. This provides the possibility of controlling high power supply voltages, and when the source is switched on, only a very short period of time is required to reach the linear operating range of the parallel control member.

Controlled power supply source

A current mirror arrangement comprising at least one input transistor of a first conductivity type, whose emitter is connected to a current supply line and whose collector is arranged to carry an input current. At least one output transistor of the first conductivity type has its emitter connected to the current supply line and its base to the base of the input transistor and from whose collector an output current can be taken. A follower transistor of the first conductivity type has its emitter connected to the bases of the input transistor and the output transistor and its base to the collector of the input transistor, and has its collector coupled to a reference potential. In order to ensure a well-defined load of the current supply line in any operating condition, the current mirror arrangement also includes a control transistor of a second conductivity type opposite to the first conductivity type. The control transistor has its collector connected to the collector of the input transistor and its emitter to the reference potential via an emitter current source. The base of the control transistor is arranged to receive a control voltage for controlling the output current. The collector of the follower transistor is coupled to the reference potential via a resistor. A further transistor of the second conductivity type has its emitter connected to the emitter of the control transistor, its base to the collector of the follower transistor, and its collector to the current supply line.

Current mirror arrangement

A circuit for testing the leakage resistance of a circuit point. Particularly in the case of circuits where safety is important, a circuit point, particularly an output terminal of an integrated circuit, should be tested for a leakage resistance relative to ground and/or a voltage to provide an early detection of an imminent failure condition. To this end, at least one test current is fed into the circuit point and the voltage at the circuit point is monitored by means of a comparator. When the leakage resistance decreases below a permissible value the voltage at the circuit point decreases, which can be detected by the comparator. For monitoring a leakage resistance relative to both poles two opposite test currents are applied and the comparator is constructed as a window comparator.

Circuit arrangement for leakage-resistance testing of a circuit point

A symmetrical amplifier includes a current mirror circuit and a current splitting circuit. The current splitting circuit splits up an input signal applied to the amplifier as a function of the signal polarity. Negative input currents are applied to the current mirror circuit whose controlled output current is applied to a control input of a first current amplifier circuit arranged in the amplifier. In order to insure symmetrical operation of the amplifier, positive input currents flowing into the amplifier are applied to a control input of a second current amplifier circuit arranged in the amplifier. The second current amplifier circuit is the same as the first current amplifier circuit. The first current amplifier circuit is connected to a positive supply voltage and the second current amplifier circuit is connected to a negative power supply voltage, and the two current amplifier circuits operate into a common load at their output ends.

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Hamburg, Germany

Axel Nathe