Design for a common source FET Amplifier Circuit - Electrical Engineering Stack Exchange most recent 30 from electronics.stackexchange.com 2019-08-25T20:26:39Z https://electronics.stackexchange.com/feeds/question/199853 http://www.creativecommons.org/licenses/by-sa/3.0/rdf https://electronics.stackexchange.com/q/199853 1 Design for a common source FET Amplifier Circuit user3479118 https://electronics.stackexchange.com/users/59734 2015-11-09T00:26:14Z 2015-11-09T00:26:14Z <p>Here's a design question our prof gave us to study for the exam. I'm having trouble putting it together.</p> <p>A common source amplifier is shown. The FET is working in saturation and has gm = 0.5mS, Kn = 0.5 mA/V^2, Vtn = 1v and lambda = 0.02V^-1. The resistance of the signal source is 2kohms. There is a maximum gain of 112, and Id = 0.24mA. The circuit has output resistance of 20.9kohm, and input resistance of 892kohms. Determine Vds.<a href="https://i.stack.imgur.com/BmJhV.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BmJhV.jpg" alt="The circuit"></a></p> <p>Alright so my thoughts when trying to come up with a solution were as follows:</p> <p>1) It's given that the MOSFET is in saturation therefore: 0.24 = 0.25(Vgs - 1)^2(1+0.02Vds) 2) We know Vd = 12 - (Rd)(0.24) 3) We know Vs = 0.24(R5 + R4)</p> <p>Also, this is DC analysis, so the capacitors act like open circuits; technically only the middle part of the circuit is off concern.</p> <p>I don't know how to take it from here; we're not given any of the resistor values and it seems like there's simply not enough equations to cover the unknowns. I presume it's got something to do with the provided input and output impedences, but I just don't know how to apply them. Any help would be appreciated</p>