Tag
analog
6 articles.
- ADC noise floor calculation: SNR, process gain and the FFT
An ideal 12-bit ADC has 74 dB of SNR; its 4096-point FFT shows a floor at 107 dB. Both are right, and the 33 dB between them is the commonest misreading.
- Resistor codes: colour bands, SMD digits and EIA-96
How to read every resistor marking, why the E-series values look arbitrary, and which codes are genuinely ambiguous — with the tolerance derived, not looked up.
- Sallen-Key low-pass filter design, without the guesswork
Pick a response shape, read its Q, and get the two capacitors and one resistor. Then the four things that decide whether the built filter matches the design.
- LED series resistor: the value, and the current you get
Compute the resistor from headroom, then find why one part number gives a 2:1 current spread on 3.3 V, what an MCU pin really delivers, and when to stop.
- 555 astable design: frequency, duty cycle and error
Size RA, RB and C for a 555 oscillator, find out why the duty cycle cannot reach 50 %, and see which of the datasheet's error terms actually dominates.
- Guard rings: stopping PCB leakage into high-impedance nodes
Gigaohm trace-to-trace resistance still leaks nanoamps at 5 V. Compute when board leakage beats V_OS and bias current, and lay out a driven guard to remove it.