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Unformatted text preview: UC Berkeley, EECS Department B. E. Boser EECS 40 HW6: Input and Output Resistance UID: Read Section 5.6 in Nilsson & Riedel 1. Photodiodes are often used as light sensors (e.g. to measure ambient illumination or as receivers in fiberoptic communication systems). From a circuit perspective a photodiode behaves just like a current source i D with output resistance R D . In practice, a voltage output is usually preferred. Without the amplifier circuit shown below, the change of the voltage across the photodiode is small and further depends on the value of R D , which itself is a function of the signal. The amplifier solves both problems. Find the value of R 1 resulting in a transresistance v o / i D of V/ A. R 1 = 1 pt. Such circuits have many applications, e.g. in electronic devices to measure ambient illumination and adjust the intensity of LCD back-lighting accordingly. Combined with an (LED) light source, this circuit can be used in an intruder alarm. Options for the class project. 2. The current into the input of an ideal operational amplifier is ideally zero. Many operational amplifiers come close to this ideal, with leakage currents in the pA or even fA range....
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This note was uploaded on 01/15/2011 for the course EE 40 taught by Professor Chang-hasnain during the Fall '07 term at University of California, Berkeley.
- Fall '07