Abstract: A high-speed current mirror and correction circuitry are provided to minimize current errors in short-channel MOS switched current mirrors. The current mirror supplies high current levels at high modulation speeds, while simultaneously exhibiting good output voltage compliance. The correction circuitry includes a buffer amplifier, current shaping circuit, and replica mirror section. The current shaping circuit is able to supply a differential reference current, to correct load current errors, in response to the replica mirror section matching the buffered load voltage.

Abstract: A cable drive circuit allows a transmitter in a process control system to drive signals across a capacitive length of cable. The cable drive circuit uses a charge pump to store charge, which is then used in conjunction with open drain outputs to transmit logic signals across a cable to a peripheral at the other end of the cable. A microcontroller or other device specifies the number of communication pulses to send across the cable before allowing the charge pump to recharge. By transmitting communication pulses for a small percentage of the time the average current is minimized, making the circuit suitable for operation under the 4-2OmA standard for two-wire devices.