Dual Picoampere Input Current Bipolar Op Amp

The AD706 is a dual, low power, bipolar op amp that has the low input bias current of a JFET amplifier, but which offers a significantly lower IB drift over temperature. It utilizes superbeta bipolar input transistors to achieve picoampere input bias current levels (similar to FET input amplifiers at room temperature), while its IB typically only increases by 5 at 125°C (unlike a JFET amp, for which IB doubles every 10°C for a 1000× increase at 125°C). The AD706 also achieves the microvolt offset voltage and low noise characteristics of a precision bipolar input amplifier.

Since it has < 200 pA of bias current, the AD706 does not require the commonly used “balancing” resistor. Furthermore, the current noise is only 50 fA/√Hz, which makes this amplifier usable with very high source impedances. At 600 A max supply current (per amplifier), the AD706 is well suited for today’s high density boards.

The AD706 is an excellent choice for use in low frequency active filters in 12-bit and 14-bit data acquisition systems, in precision instrumentation, and as a high quality integrator. The AD706 is internally compensated for unity gain and is available in five performance grades. The AD706J is rated over the commercial temperature range of 0°C to +70°C. The AD706A is rated for the extended industrial temperature range of −40°C to +85°C.

The AD706 is offered in two varieties of an 8-lead package: PDIP and surface-mount (SOIC).

PRODUCT HIGHLIGHTS

* The AD706 is a dual low drift op amp that offers JFET level input bias currents, yet has the low IB drift of a bipolar amplifier. It may be used in circuits using dual op amps such as the LT1024.

* The AD706 provides both low drift and high dc precision.

* The AD706 can be used in applications where a chopper amplifier would normally be required but without the chopper’s inherent noise.

APPLICATIONS

* Low Frequency Active Filters

* Precision Instrumentation

* Precision Integrators

* High DC Precision

* 100 µV Max Offset Voltage

* 1.5 µV/°C Max Offset Drift

* 200 pA Max Input Bias Current

* 0.5 µVP-P Voltage Noise, 0.1 Hz to 10 Hz

* Quad Version: AD704