Abstract: A digitally trimmed current source. The novel current source includes a first circuit for generating a current in response to an applied voltage and a resistance variable in response to a control signal, and a second circuit for supplying the control signal. The first circuit includes a resistive network comprised of a plurality of resistors; a plurality of switches, each switch coupled to one of the resistors and adapted to selectively switch the resistor in and out of the resistive network in response to the control signal; and a transistor adapted to apply a voltage across the resistive network to generate a current.

Abstract: A DAC (10) including an operational amplifier (12) having an input terminal; a plurality of current paths coupled to the input terminal; a plurality of current sources (I1/2 -I4/2); and an arrangement (11) for switchably coupling current from at least two of the cells to a respective one of the paths in response to an input signal. In a specific embodiment, the inventive DAC (10) further includes a first resistive element (2R1-2R4) disposed in each of the current paths, a second resistive element (R1-R4) disposed between the current paths, and a feedback resistor (RF) disposed between an output terminal of the amplifier and the input terminal thereof. In the illustrative embodiment, the coupling arrangement includes a plurality of switches (SW1-SW4); each of the switches is adapted to switch half of the current from a first source and half of the current from a second source into a respective one of the paths.

Abstract: A digitally trimmed current source. The novel current source includes a first circuit for generating a current in response to an applied voltage and a resistance variable in response to a control signal, and a second circuit for supplying the control signal. The first circuit includes a resistive network comprised of a plurality of resistors; a plurality of switches, each switch coupled to one of the resistors and adapted to selectively switch the resistor in and out of the resistive network in response to the control signal; and a transistor adapted to apply a voltage across the resistive network to generate a current.

Abstract: A current switch. The novel current switch includes a differential pair of transistors Q1 and Q2, a pair of cascode transistors QA and QB coupled to Q1 and Q2, respectively, and a circuit for maintaining QA and QB in an ‘on’ state regardless of the states of Q1 and Q2. The circuit for keeping QA and QB on includes first and second current sources adapted to supply first and second trickle currents to the emitters of QA and QB, respectively. The bases of QA and QB are connected in common to a voltage source VREF4, which, in an illustrative embodiment, is implemented using a Schottky diode for lower impedance. The circuit for driving Q1 and Q2 may also be implemented using a current switch with trickle current, cascode transistors Q14 and Q15 to further improve settling times.