An MOS field-effect transistor having its gate electrode connected to its drain electrode can be used to operate as a constant current device by means of a resistive network placed between its source and substrate electrodes.
A first semi-conductor has a first threshold voltage and provides a particular voltage drop across it in its saturated state of operation. A second semi-conductor has a second threshold voltage and provides the particular voltage drop across it in its saturated state of operation. The second semi-conductor may be a native device. The first and second semi-conductors are connected to provide a common flow of current. A current is induced, as by a third semi-conductor, to flow in the second semi-conductor. The first and second semi-conductors are commonly biased to produce a flow of saturated current through them when a current is induced to flow in the second semi-conductor. Each of the first, second and third semi-conductors may be provided with a gate, drain and source. The sources and drains of the semi-conductors may be in series. The gates of the first and second semi-conductors may be commonly biased and the gate of the third semi-conductor may be biased to produce the flow of current through the second and third semi-conductors. A circuit may be connected across the first semi-conductor and may be provided with first and second states of operation. In the first state, the saturated current flows through the third, second and first semi-conductors and, in the second state, the saturated current flows through the third and second semi-conductors and the parallel circuit. The parallel circuit may be included in a digital-to-analog converter in which bits are disposed in rows and columns and in which an analog value is produced by activating bits in selected rows and columns.
Unity current gain impedance transformation at the input of a field effect transistor current mirror amplifier reduces the input impedance and renders it independent of the mirror ratio. A net saving of semiconductor material may be obtained for a given mirror ratio and input impedance when the transformation is provided by a common gate connected complementary field effect transistor meeting certain effective threshold voltage and forward transfer conductance ratio requirements.
A differential amplifier suited for use in operational amplifiers employing both FET's and junction transistors has a superior gain-bandwidth product for given input offset specification. Source-coupled FET's accept input signals at their gate electrodes. Each FET is included in a composite transistor device together with a direct coupled, inverting, current amplifier having an input terminal to which the drain electrode of the FET is coupled and having an output terminal coupled to the source electrode of the FET.
A voltage regulator for a battery power source capable of maintaining a predetermined voltage until the battery voltage decays to very nearly the predetermined voltage uses a bipolar transistor in series with the battery as the control element in series with a zener diode and a resistor. A field effect transistor between the base of the bipolar transistor and a junction between the zener diode and resistor regulates base current of the bipolar transistor, thereby to regulate the conductivity of the bipolar transistor for control of the output voltage.
