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Hi all,
I am working on a scale system that is powered and communicated with PC using USB. The system I am using has MSP420F2013 from TI. I am kind of new with USB stuff, only used serial to USB converter before not building one. I am reading about FDTI USB chip but not sure which one is the...
Re: Pspice model request
Hi abbeyromy,
Thank you for your replying. I know how to create a model with provided spice model from the manufacture. However, I dont know how to create one base on datasheet. I dont know how to obtain the parameters like W,L, RS, UO, IS, CGSO, NFS, etc.
Those FETs...
Pspice model request
Can anyone show me how to make these models:
P-MOSFET:AO3423
N-MOSFET:AO3424
LED: SFH4231
and photo transistor: PT501
I would like to learn how to create PSPICE model base on datasheet. For example: where to look for parameters: IS, N, RB, PHI, GAMMA, DELTA, ETA,etc...
Just quick question...
What is the output of this circuit? (suppose Vdac=0=GND)
Ip=Current Photo
will it be Vo= -Ip * R
or Ip*R?
And why? Because someone told me it should be -Ip*R not Ip*R. And most of transimpedance circuit use in different configuration.
I am getting confused here...
What do you mean by "partly working"? My purpose is to detect the intensity of a light.
So I should take out R2 and replace R1 to 5k to have the gain of 5 of the photo current? And if I put Vref=0, it should be exactly as the circuit above (Photodiode circuit)?
1 more question. I have seen...
Here is my analysis:
Vp: + input of opamp)
Vn: - input of opamp)
Vo: output
Vp=12*800/(800+800)=6V (DC) (voltage divider)
Vn=Vo*100/(100+200)=1/3*Vo
Vp=Vn (Opamp)
=> 1/3*Vo = 6V => Vo=18V which is not right because Vs=12V, it does not have enough power to put Vo up to 18V, therefore what u...
OK, so now I have phototransistor (PT) instead of photodiode (PD)...Can anyone tell me if this circuit is wrong?
Here is my analysis, when a light strikes PT, it will create a Photo current from collector to emitter. Direction of current should be Vo->Vn->V1
(Vo-Vref)/R1 = (Vref-V1)/R2
<=>Vo...
Re: LEDs Switching
When looking for FETs in digikey.com, I saw there is an option "Rds On (Max) @ Id, Vgs". For example: 12mOhm, 11A, 4.5V. How do you interpret this option?
What I understand is: Vds=Rds*Id=12mOhm * 11A =0.132V
At the V-I curve of FET, the curve will "bend" at 0.132V (Vds)...
I think I have an answer for the PD problem. As circuit shows: Vn=Vp=0, which creates zero voltage across the D1 (and always be, because of the opamp). Which means PD is in reversed bias, or in photo conducting mode. Therefore, when a light strike the PD, it will create photocurrent (Id) flows...
So the book was wrong!!! The confusion here is the direction of current. I was confused.
Ok, so I have 1 more analysis for opmap. V1, V2 are inputs. Assume ideal opamp, and here is my calculation:
(Vo-Vn)/R1 = (Vn-V1)/R2 <-----Here is the confusion part, what should it be Vn-V1 or V1-Vn...
Hello all,
I have confusion when analyzing this simple basic circuit:
I have a circuit that amplify the signal from a photodiode (D1) with a opamp U1 and R1. Here is my calculation for Vo: (suppose ideal opamp)
When there is light, D1 creates current Id, whose direction goes from D1 to Vn...
Re: LEDs Switching
Thanks for the reply,
So for switching application what parameters do I need to know when choosing a FETs? Like you said Rds (on). What else? And can you explain those parameters?
Dual power supply is easy to work with cause you dont need to create "virtual ground" (mid point of Vcc). However, as you said single power supply is easy to design. But to have OPAMP works with single power supply you have to create mid point voltage so the AC (or small voltage you said) will...
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