Power Electronics
Femtoamp Bias Current Op Amps Achieve 500 MHz Gain Bandwidth

Femtoamp Bias Current Op Amps Achieve 500 MHz Gain Bandwidth

The LTC6268 and LTC6269 FET-input single and dual op amps from Linear Technology are rated for 3 fA bias current at 25 °C and 4 pA max over the entire -40 °C to 125 °C temperature range. They can resolve input currents from several femtoamps to amps. Wideband voltage and current noise is 4.3 nV/Hz and 5.5 fA/Hz , respectively, enabling high dynamic range circuits. Built for speed as well as precision, the LTC6268 features 500 MHz gain bandwidth product, sub-pF input capacitance and -100 dB harmonic distortion at 1 MHz. In addition to photodiode and photomultiplier (PMT) circuits, the LTC6268/9 are well suited for other high impedance sensor applications and for driving analog-to-digital converters (ADCs).

The LTC6268 data sheet features circuit and layout techniques to maximize TIA performance, with example circuits ranging from 20 kW transimpedance gain at 65 MHz bandwidth, to 499 kW transimpedance gain at 11.2 MHz bandwidth.

The LTC6268 is available in a 6-lead SOT-23 package, as well as an 8-lead SOIC with guard pins to protect against board leakage currents. The LTC6269 is available in MSOP-8 with exposed pad and 3mm x 3mm DFN-10 packages.

The LTC6268 and LTC6269 are unity-gain stable and fully specified over the industrial -40 °C to 85 °C and -40 °C to 125 °C temperature ranges. Prices start at $2.90 each for the LTC6268 and $4.90 for the LTC6269 each in 1000-piece quantities.

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