This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 1 Lecture 4 Operating Point Calculations Operating Point Calculations A Look at the Inner Workings of Spice R. Dutton, B. Murmann R. Dutton, B. Murmann 1 EE114 (HO #7) Stanford University Operating Point Calculations Calculating the operating point in the amplifier example from last lecture was relatively straightforward Assume transistor operates in saturation region Compute drain current (via a simple closed form expression) Check if result is consistent with assumption (V DS >V GSV t ) If not, repeat calculation with triode equation Computing the operating point in general, and in more complex circuits can be difficult Primarily due to the transistors nonlinear IV characteristics and because their region of operation is not known a prior R. Dutton, B. Murmann 2 and because their region of operation is not known a priori To give you a better feel for this issue, we will work through a slightly more complex circuit And take a look at how Spice handles the calculation EE114 (HO #7) 2 Example Given: V I =2V, W=20 m, L=1 m, R 1 =5k , R 2 =25k , V DD =5V Device parameters: C ox =50 A/V 2 , V t =0.5V Calculate: I D V DD R 2 V o W/L V i Note: This circuit is called a common source amplifier with source degeneration. In this lecture we will only analyze the DC operating point of this circuit. You will take a closer look at its sma signal R. Dutton, B. Murmann 3 EE114 (HO #7) R 1 take a closer look at its smallsignal transfer function in homework 2....
View
Full
Document
 '08
 MURMANN
 Amplifier

Click to edit the document details