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15 Threads found on edaboard.com: Bias Telescopic
Hi guys I need to bias a telescopic opamp with input and output CM at 0.9V. Currently I am not able to bring the transistors in saturation by using voltage sources for biasing. What kind of current mirror circuit can I use? Please help. Thanks!
if u are using a basic current equation i=beta*w/l*(vgs-vth)^2 to calculate w/l then the you will have problems. at 0.18u the first order eqn is not so valid. i suggest you setup a testbench ( connect a current source into a diode connected device to setup ur bias and then have a mirror device whose w and vds u can vary to keep it in saturation). t
proper bias is to keep every transistor in saturation region。 try to find the poles and zero of the 2-stage amplifier. i think the book entitled analog design essentials by Sansen has elaborated the design procedures systematicly.
There are three high-swing biases: why the last one is sensitive to body effect? and the others is less sensitive to body effect? could anyone help me to solve this problem? i will choose one of these circuit to bias my telescopic OTA. help me please. thank you for your help.
for the input common mode level and the bias voltage V_B1 , V_B2 and V_B3. It must be chosen so as to allow maximum output swings. for the design using Hspice ********** AOL, GBW, PM SETUP ********** Vin1 0
a cmos telescopic cascode OTA for hi swing, low power application? replica bias? Please advice! Thanx
a cmos telescopic cascode OTA for hi swing, low power application? replica bias? Please advice! Thanx
check if your cmfb output to bias current is right? because of Vds effect, bias current may be not very exactly.
mainly check ur bias, try to decrease the overdrive voltage
if you give an extremely large input , your common mode will be disturbed and your bias will be the input should be as small as possible. Tell us what is the configuration of the opamp you are trying to use, i mean two stage , folded cascode, telescopic etc. The gain for each of these are different. You can also refer to johns and martin
Hi could some one upload a nice tutorial for design bias circuit for telescopic, realy i have problem in design it regds Added after 25 minutes: hi every body here i have the circuit Vthp=0.56 vthn=0.54 vdsat3=100e-3; vdsat5=153.34e-3; vdsat7=575e-3; vdsat11=276.9e-3; vdsat13=100e-3;
for 1.8v telescope op, it is hard to bias input common -mode voltage to 0.9v, although you want common-mode voltage for each stage to be same, but i don't think it need that the input and output common-mode voltage should be same.
The statement is only true for single-stage amplfier (such as folded-cascode or telescopic). For two stage amplfier, the slew rate does depend on both the input stage bias current and output stage source/sinking current capability.
Hi wedd, Can you post your simulation result online? If you want, you can post your the schematic and bias condition as well. Maybe that will help!
It depends on your structure and it will be very difficult to design it with, say telescopic opamp, but with two-stage opamp, I think it's still viable. Also, the bias opoints have some effects on it.