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Flyback source and magnetic air gap – I was studying dc-dc converters because I want to do a flyback voltage source. There’s a circuit which ON Semiconductor gives that does all the calculus but there is something missing and it’s the ferrite core. What I found it that in the flyback’s switching source the analysis of the transformer is more like a couple inductance. There is a difference between a transformer with a couple inductors? I do not understand why there is an energy storage, which displays for a difference of phase between the primary and secondary voltages and in a simple transformer at 60Hz does not. Read more
Differential to single-ended and no common mode feedback – Why is the output common mode voltage only a concern in fully differential circuits? Why is there not a requirement to keep the output bias voltage at a required level in a circuit with only a single output (like the common diff. amp with a current mirror load? Read more
MC145151 in all bands HF PLL oscillator – I have found this PLL circuit with a variable frequency oscillator for HF, which seems straightforward and does not require any programming (important to me) and the output is sinewave. I would like to use it in a direct conversion transceiver for all HF bands and I wonder about some points:
1. How to order this rotary encoder, what type is it, how to ask for it at the electroncis shop?
2. In the example, the step size is 1KHz. What configuration of switches and crystal must I choose, so that this step size can be decreased? I only need 200KHz for each HF band.
3. Can I just use the 1KHz step example and manually trim the 8.192Mhz crystal oscillator frequency with a capacitor, to fine tune the VCO? In that case, an estimation of the range of the fine tuning? Read more
Low-cost alternative to OPA197 – The OPA197 is a nice opamp. Many other op amps beat it in specific areas but the OPA197 has a well-balanced set of all-around good specs. But, at ~$2 apiece, it’s a bit pricey to keep as a general stock part. I’m wondering if anyone here can suggest a lower-cost alternative. Read more
Flyback PSU instability problem – I am testing a flyback converter that uses the LM5021Oh IC. I have an issue where at some load / Vin combinations every other PWM pulse is a different width. I am using the IC variant that allows 50% duty cycle max and as far as I can see, for example, one pulse might be close to 50%, the next 30%, then 50% and so on. I wouldn’t have thought it would be the Voltage feedback loop but I have slugged that anyhow, with no effect. Read more
Single-mode audio spectrum inverter problem – I’ve attached two images. One is a single-mode audio spectrum inverter and the other one is a dual-mode (two stages). As far as I am aware the dual stage should suppress the carrier and the unwanted sideband. However, the single mode is attractive due to its simplicity.
What is the purpose of the transformer in the single mode circuit? Read more
Current source to simulate load transients – Can someone tell me what’s the best way to have a current source to perform load transient simulations? I could use IDC source but that’s an ideal source and that could lead to massive voltage at its terminals. Read more
