AD588 Precision Dual Reference Output Buffer

About this circuit

# AD588 Precision Dual Reference Output Buffer ## Application This circuit uses AD588 as a split-supply precision reference with its two output amplifiers wired as unity-gain buffers. It is a practical starting point for bipolar calibration references, ADC/DAC reference drive, and precision analog systems that need matched positive and negative reference outputs around ground. ## Design Context VPOS provides +15 V and VNEG is wired as a 15 V source from ground to the negative rail, so U1 sees +15 V and -15 V supplies. U1's VCT, BAL_ADJ, and GND_SENSE_N pins are tied together as the driven center-tap node, while GND_SENSE_P is tied to the common return. The A3 buffer input is driven from the internal VHIGH node, while A3_FORCE and A3_SENSE form the buffered positive output. The A4 buffer input is driven from VLOW, while A4_FORCE and A4_SENSE form the buffered negative output. CNOISE provides a 1u noise-reduction capacitor and RGAIN parks the gain-adjust pin through a 1G high-impedance return. ## Expected Behavior Vhigh should settle near +5 V, Vlow should settle near -5 V, and Vct should remain near 0 V. RHIGH and RLOW are 10K output loads, so each buffered reference output sources or sinks about 0.5 mA at the operating point. ## Key Values - VPOS: +15 V DC supply. - VNEG: 15 V source oriented to create the -15 V rail. - RHIGH and RLOW: 10K output loads. - CNOISE: 1u noise-reduction capacitor. - RGAIN: 1G high-impedance gain-adjust return. - Measured outputs: Vhigh, Vct, and Vlow. ## Suggested Experiments - Change RHIGH or RLOW to compare positive and negative output loading. - Remove or change CNOISE when comparing startup/noise-filtering behavior in a transient run. - Replace RGAIN or the balance-adjust connection with trim networks when adapting the circuit to a precision calibration application. ## Featured Component AD588 Voltage Reference is the precision dual-output reference under test. The demo highlights the distinction between the internal VHIGH/VLOW reference nodes and the buffered A3/A4 force-sense output connections.