Classic analog circuit diagrams worth collecting

As electronic people, we usually need to come into contact with different circuits, but there are some circuit diagrams that are classic and worth remembering forever.

bootstrap

The circuit is used in the sample circuit before various ADCs, which allows the ADC to realize rail-to-rail input. The working voltage of the sample circuit exceeds Vdd, which greatly reduces the setting time and has almost no reliability problems. No component in the circuit can be reduced or moved. This circuit directly made the development of ADC a big step forward. Now it has almost become the standard configuration of various ADCs except ΔΣ, and has become one of the most classic analog circuits in history. Of course, the circuit principle is not easy to understand at first glance.

The working waveform looks comfortable:

a magical current source

Enter 'any' current. (The quotes mean, for any current value of reasonable size), the output will be approximately 2*ln8*Vt/R.

SAR-ADC

Here’s how it works:

At each clock edge, the comparator compares the voltage on the capacitor with ground, and uses the result to determine whether the next capacitor should be connected to the circuit.

In essence, it is to use the dichotomy method to approximate an unknown voltage.

structure

Capacitor terminal voltage change

Premium version

switch cap CMFB

Only 4 capacitors and 6 switches realize CMFB, which is very simple and will hardly affect the OPAM itself like output swing, gain and other specs. It is very efficient.

Data Weighted Averaging

The basic idea is to quickly traverse each current element in the DAC to reduce the impact of current element mismatch on the ADC signal-to-noise ratio. It is very clever to achieve first order noise shaping of current element mismatch through just a few simple digital modules.

Universal H-bridge circuit

The drive motor rotates forward and reverse, which is very easy to use and affordable. The cost of buying a driver chip is enough to build ten bridges by yourself. And it can be done with the most common triode on the market. If the power is slightly higher, just replace it with a MOS tube.