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Thanks for the quick response FvM.
Yes thats exactaly what the issue was, the conductance of the internal protection diodes on the SPI lines when the power was switched off by the P-MOSFET caused the 3.8V on the ADC supply. I had spoken to a colleague and he suggested the same thing. I've now...
Hi,
I'm having trouble with switching off a P-Channel MOSFET which supplies power to an ADC (please see attached schematic). The idea was a "belt and braces" measure to ensure we could cycle the power of the ADC as this particular part has know to hang-up.
Although the p-mosfet is switching...
Theres also a number of free classes from spring 2007 to view now (including lecture notes) from the same professor at MIT which I thoroughly recommend!
MIT OpenCourseWare | Electrical Engineering and Computer Science | 6.002 Circuits and Electronics, Spring 2007 | Video Lectures
For anyone who's interested MIT will provide a free analog design course commencing March 2012, see link below for more details:
BBC News - MIT launches free online 'fully automated' course
As the guys above have stated, because your using common mode on your supply (i.e. between GND-3.3V) the output won't go below 0V or above 3.3V. As suggested previously you need to increase your supply voltage to >4.5V, ideally 5V to give you some head room.
As far as achieving the output range...
Guys thanks very much, i'm still lost as i can caluculate both -0.9V from Checkmates equation (and on wiki) and 1.8V on LvW's
Can I use a diff amp with the inputs inverted, i.e. with the input wires on my diagram the other way around
LvW, that sounds more like what i'm seeing!!
ahh right i see, so what would you recommend if i wanted to increase the resolution of a voltage range between 2.59v-3V and expand out to 0-5V.
Its actually a 10K resistor to a RTD but i'm not simulating that and just have 20k on Rg
So where did...
Oh sorry theres another 10K on the input Vin- else where on the circuit.
My tutor has said that the output would be inverted which is whats happening, as you increase int input voltage on V2 2.59V-3.00V the value decreases, but i don't understand why?
V1 = 2.5V (Vin+) and V2 = 2.59 (Vin-) which ok would give me -0.09V*10 = -0.9V but my sim is giving 1.6V??
Is my circuit correct or have i missed anything out?
Hi Guys,
I have a differential amplifier circuit with a voltage input range of 2.95-3.00V and I wanted to expand the range by using the differential amp with 2.5V on the +ve input of the amp and using a gain of 10 to give me a range of 0.9V to 5V at 0.1V steps.
The issue I have is that when i...
Guys,
I've noticed quite a few posts discussing RTD's and implementing them to a Microcontroller by use of buffer/differential amps. My question is do you really need the buffering? Can I not just add the RTD as a voltage divider circuit to the micro to provide the voltage swing to the Micro...
OK I understand in principle what your saying, I just don't understand the reason for this action, surely the easiest route for the current path to take (from the energy stored in the inductor and cap) would be through the load (RL)?
I have used TINA in the past with proven circuits and the simulator displays no output, so i'm very dubious to use TINA again, try using the 30day B2 Spice it seems more reliable and is frequently updated (I can't remember the last time TINA had an update)
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