A method of operating a circuit such as an integrated circuit carried on a plastic card which includes the steps of accepting a challenge, and generating a first response to the challenge using a first algorithm which operates on at least the challenge and a secret key derived from information relating to the circuit. The challenge may be generated, and accepted, by the circuit, with a corresponding challenge being generated externally of the circuit. Alternatively, the challenge is generated externally of the circuit and is then accepted by the circuit. A token count may be stored in the circuit and the first response is generated if a decrement command is successfully carried out on the token count.

Secure token integrated circuit and method of performing a secure authentication function or transaction

A linear voltage-to-current converter (LVCC) circuit includes two transistors, one P-channel and one N-channel. The input voltage is applied to the gates of both transistors. The drains of the two transistors are connected. The source of the p-type transistor is connected to a first voltage rail, and the source of the N-channel is connected to a second voltage rail of lower voltage. The output is the difference between the current through the P-channel transistor and the N-channel transistor. A linear current-to-voltage converter (LCVC) circuit is similar to the LVCC circuit, except that the gates of the transistors are tied to the drains of the transistors. The input current is supplied to the drains, and the output voltage is the voltage of the drains.

Circuits for linear conversion between currents and voltages

A circuit for compensating for MOS device response to supply voltage variations, as well as temperature and process variations, in an integrated circuit device. The compensation circuit produces a reference voltage which modulates the gate bias voltage of a MOS transistor such that the gate-to-source bias of the MOS transistor is varied to compensate for variations in the supply voltage as well as for variations in the temperature and manufacturing process. The circuit pulls up the reference voltage toward the supply voltage as the supply increases, thereby increasing the gate drive on the MOS transistor. The circuit provides compensation for both AC and DC supply variations. The MOS transistor is used to modulate the available current sinking capability in an IC device output buffer, such that as the MOS gate drive increases, the current sinking capability is reduced, thereby slowing the output state transitions as the supply increases, and reducing noise caused by supply variations.

Noise reduction output buffer

Method for altering an electrical characteristic of a circuit having at least one active semiconductor device involves applying at least one pulse--a voltage pulse, a current pulse, an energy pulse, or a power pulse and so forth--across the active semiconductor device, the pulse having sufficient amplitude of one or more of its electrical parameters and time duration to alter the electrical characteristics of the device, and thereby, the electrical characteristic of the circuit. The pulse is applied across the junction by applying it to at least one terminal or electrode which is contacted to semiconductor material disposed within the device. In a preferred embodiment of the inventive method, the amplitudes of the electrical parameters and the time duration of the at least one pulse should be high enough to ensure that dendrites or filaments of material from the electrode are formed in the semiconductor material of the active semiconductor device but whose dendrites or filaments are not of a geometry to cause a short cricuit to be formed between any pair of electrodes of the active semiconductor device.

Method for altering characteristics of junction semiconductor devices

A digital frequency synthesizer for synthesizing a selected frequency or a library of preselected frequencies in which a selected phase increment is fed at a clock rate to an adder and accumulating register in mutual cooperation as a digital integrator, the resultant period overflow of the register corresponding to the selected frequency of interest. An improvement is provided for reducing discrete spectral spurs in the spectral output of the synthesizer by means of preselectively randomly jittering the input to, or output of, the register, whereby the average periodicity of the register overflow for a selected frequency is not affected.

Digital frequency synthesizer with random jittering for reducing discrete spectral spurs

A voltage to current converter circuit manufactured with a MOS process generates a linear reference current over a wide bandwidth and operates with an input signal that varies to either supply rail. A voltage divider network scales an input voltage for conversion to a linear current by a cascode current mirror and a gain resistor. The value of the gain resistor determines the transconductance of the conversion from voltage to current. A second current mirror provides feedback to keep the reference current accurate. An output stage makes available high impedance source and sink current output terminals wherein a source current and a sink current relative to the reference current are provided. Several voltage to current converter circuits may be coupled together to provide a addition, subtraction, multiplication, and other circuit and system functions.

MOS voltage to current converter

In a method of electrically altering the characteristics of a semiconductor device, a lateral polysilicon zener diode's zener knee voltage may be shifted either to a higher or lower voltage. An electrical potential may be applied in the forward direction to shift the zener knee to a higher voltage level. An electrical potential may be applied in the reverse bias direction to shift the zener knee to a lower voltage. In the limit, the zener may be changed into a forward diode of reverse polarity with respect to the original zener. The electrical potential used should be of appropriate magnitude to melt the polysilicon without damage to the zener's terminals. This induces migration of the impurities causing a rediffusion of impurities thereby altering the characteristics of the diode. This method may be used to program a PROM by either converting the zener to a diode or not to program each binary bit. The device may also be used as an analog memory element by setting an entire word equal to a predetermined zener knee voltage.

Method of electrically adjusting the zener knee of a lateral polysilicon zener diode

The accuracy of a required tone set, digitally synthesized by a microprocessor, is improved beyond the theoretical limit of the microprocessor circuitry by producing each tone at a frequency which is a sub-multiple of the desired frequency, then multiplying to provide the desired frequency. With the addition of a multiplier such as a doubler, a better choice of oscillator frequency becomes possible which further increases the tone frequency accuracy. The microprocessor can also reduce the start up time and the time between tones, eliminating delays in transmitting a series of coded tones.

Microprocessor tone synthesizer with reduced quantization error

A crystal oscillator comprising a crsytal and an inverter amplifier which utilizes a current mirror to provide a voltage output having a frequency double the frequency of the voltage waveform present in the inverter amplifier.

James T. Doyle

Papers

MOS voltage to current converter

Method of electrically adjusting the zener knee of a lateral polysilicon zener diode

Microprocessor tone synthesizer with reduced quantization error

Frequency doubling crystal oscillator via a current mirror