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ass7_w2011 - ECE 100 Lab 7 Design of a Mixed-Mode...

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ECE 100 Lab 7 Design of a Mixed-Mode Oscillators Winter 2011 The Wein-Bridge oscillator is a very good low-frequency sinusoidal oscillator. However there are many applications where higher frequencies are needed and often, for example for digital clocks, a pure sinusoidal waveform is not needed. In this lab we will test two widely used oscillators which are partly digital and partly analog (or mixed-mode) circuits. We will also use an opamp, the LM301A, in which the internal compensation pins are accessible to improve its performance as a Schmitt trigger. 1. The Ring Oscillator: The ring oscillator is simply a ring of N digital inverters each output connected to another input. To oscillate N must be an odd number N 3. It is often used as a test circuit on VLSI chips where N might be several 100s. The period of the oscillation depends on the delay time of the inverter T D as P = 2 N T D . If the HL and LH delay times are different one uses the average delay in this expression. We will use an antique CMOS chip, the CD4069, which contains 6 inverters. (a) Measure the time delay of the CD4069 in both HL and LH transitions (defined by the output transition) at a supply voltage V DD of 5v. To do this properly the device under test (DUT) should be between two identical inverters (a driver and a load). This way the delay time is typical of the inverter as operating in a larger digital circuit. The delay
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