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Class D works
As mentioned yesterday in Class D instead of class AB, I tried making a class D amplifier out of the one-op-amp amplifier I had built before, adding a comparator comparing that value with a triangle...
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Eleventh day of circuit class
In today’s class, I planned a discussion of amplifiers. Because several students were late getting to class, I started with an informal request for suggestions for the phototransistor and FET lab. I...
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Thirteenth day of circuit class and first op-amp lab
If you’re wondering what happened to the 12th day of circuits class, that was discussed in Quiz too long and too hard. On Wednesday, I did some do-now problems to check on some basics and to provide a...
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Fourteenth day of circuits class
Today’s class started with another do-now problem: What is the voltage gain of the following circuit? This circuit was intended to be more of a hook than as a test of former material, though they’ve...
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Fifteenth day of circuits class
Today’s class started with two more do-now problems: What are the voltage gains of the following circuits? This problem was almost identical to one they’ve seen before. The only changes are the...
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Sixteenth day of circuits class
Today’s class started with one do-now problem: what does the following circuit do? I gave them a hint: try to decompose the circuit into parts that you already understand. No one really felt that they...
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Eighteenth day of circuits class
Today’s class started with two do-now problems: The first circuit should have been easy for the students, but the second one was brand new to them. I had expected the first circuit to be easy for them...
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Nineteenth day of circuits class
Today’s class started out well, but ended up with one of the worst lectures of the quarter. I had three topics I wanted to cover today: proper use of electrolytic capacitors strain gauges...
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Class D with LC filter works
I had a class-D amplifier working at the beginning of January, but I’ve changed the specs a bit since then (adding the LC filter) , and the students have a different comparator chip than I used then...
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Twentieth day of circuits class
We started today with a do-now problem, asking what the following circuit does: After 5 minutes, no one had any idea, so I asked questions until we got that In had a voltage of 0V, that the interesting...
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Twenty-fifth day of circuits class
I started class today with a do-now problem: What is the gain at 0Hz? ∞Hz?At what frequencies does the behavior change? Only a couple of students had any clue how to do this problem, though they’ve had...
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Twenty-sixth day of circuits class
I started today with feedback on the writing. The students have been getting much better about the content and organization of their reports, and the writing is pretty good from at least half the...
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Tried EKG design on protoboard
I built and tested an EKG circuit today using the protoboard that the students will use on Thursday, to make sure that there are no probems. I decided to try out a circuit that uses active feedback for...
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Action potential lecture and EKG lab
I did not lecture on Wednesday, but had a guest lecturer from the biology department, who gave a lecture on action potentials, based on a similar lecture she gives in a neuropsychology course. The...
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Twenty-eighth day of circuits class
Yesterday’s lecture was a mish-mash of odds and ends that we hadn’t covered well previously, and questions that had come up. I started with talking about where the EKG signal comes from. The guest...
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Supplemental sheets, draft 3
This post updates and replaces the Supplemental sheets, draft 2. It reflects the redesign of the course based on running a prototype version of the course in as a group tutorial in Winter 2013. Lecture...
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2-op-amp instrumentation amp
Last summer, I tried building an instrumentation amp using the MCP6002 op amps and external discrete resistors, and ended up with an amplifier that had terrible common-mode rejection, which is why I...
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3-op-amp instrumentation amp
Yesterday in 2-op-amp instrumentation amp, I worked through the analysis of the differential gain and common-mode gain for an instrumentation amp made from two op amps. There is a classic design of an...
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Common-mode noise in EKG
In 2-op-amp instrumentation amp, I said I’ll have to make some measurements later this week to see how large the common-mode noise on the EKG signals really is. Of course, it is likely to be highly...
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Some failed designs
For the past couple of days I’ve been exploring variations on the Blinky EKG project, looking at alternative approaches. For example, I looked at the possibility of eliminating the most expensive part...
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