Current-Feedback Op Amps Save Power In Photodiode Apps

Sept. 30, 2002
Current-feedback amplifiers offer high bandwidth with minimal power-supply current draw. However, they're rarely used as transimpedance amplifiers in photodiode applications due to the high current noise of their inverting inputs. The ...

Current-feedback amplifiers offer high bandwidth with minimal power-supply current draw. However, they're rarely used as transimpedance amplifiers in photodiode applications due to the high current noise of their inverting inputs. The figure shows how to take advantage of the 400-MHz (unity-gain) bandwidth of the LT1396 current-feedback op amp in photodiode applications while avoiding inverting-input current noise.

The photodiode is connected to the noninverting input of amplifier a of the dual LT1396 in a gain of 2. Amplifier a's output drives the inverting input of amplifier b through R1, which is selected for optimal time-domain response. Feedback resistor R2 sets the transimpedance gain at 3.01 kĦ, and C1 compensates the photodiode capacitance.

While risetime was measured at 6 ns (10% to 90%), bandwidth was modeled in Pspice at 75 MHz, assuming a 3-pF photodiode. For an 8-dB noise figure, output noise spectral density was 18 nV/ãHz, consistent with the 6-pA/ãHz noninverting input current noise and the 3-kƒ¶ resistance. To minimize board-space usage, select the MSOP-packaged version of the LT1396.

Sponsored Recommendations

Understanding Thermal Challenges in EV Charging Applications

March 28, 2024
As EVs emerge as the dominant mode of transportation, factors such as battery range and quicker charging rates will play pivotal roles in the global economy.

Board-Mount DC/DC Converters in Medical Applications

March 27, 2024
AC/DC or board-mount DC/DC converters provide power for medical devices. This article explains why isolation might be needed and which safety standards apply.

Use Rugged Multiband Antennas to Solve the Mobile Connectivity Challenge

March 27, 2024
Selecting and using antennas for mobile applications requires attention to electrical, mechanical, and environmental characteristics: TE modules can help.

Out-of-the-box Cellular and Wi-Fi connectivity with AWS IoT ExpressLink

March 27, 2024
This demo shows how to enroll LTE-M and Wi-Fi evaluation boards with AWS IoT Core, set up a Connected Health Solution as well as AWS AT commands and AWS IoT ExpressLink security...

Comments

To join the conversation, and become an exclusive member of Electronic Design, create an account today!