# Tag Info

### What's is this? An SMD Voltage Regulator?

Ti part marking lookup yields a result with LFNB. This leads to LP3981IMM-3.3/NOPB, which seems to be compatible with your pictures in terms of pinout.

### µA723 output Zener diode: why is it as high as 6.2 V?

Here's a more mechanical and internal-design explanation, if you like: Zeners around 6V are typical for vintage IC processes (and still today, I suppose, in applicable bipolar or BiCMOS processes). ...
Accepted

### µA723 output Zener diode: why is it as high as 6.2 V?

Because of physics. Turns out that around 6-7 V is the voltage for which the temperature coefficient of Zener diodes is minimized. Much lower voltage Zener diodes also operate on a different principle ...

### Instructables DIY current limiter circuit

As the circuit shows, a FET, supplied with a constant VGS, is a reasonably current source, for reasonable values of 'reasonable'. Several caveats. VGSth is thermally sensitive. The current will drift ...

### DIY Voltage and current regulator

FWIW, here's the circuit in the video: simulate this circuit – Schematic created using CircuitLab This circuit is not a "regulator" in any sense of the word. It is a simple emitter-...
1 vote
Accepted

### What are the loop gain and the transfer function of this transconductance amplifier feedback circuit?

Here is my approach for a (rough) loop gain calculation: The loop is opened at the base node of T2 The voltage gain at the collector node of T2 is G=v_c2/v_b2=-(1/2)gm_2 * r_load * 2=-gm_2 * r_load. ...
1 vote

### Microwave oven control board not working

From the pictures I assume the schematic looks like this. A negative linear voltage regulator LM7905 is used, not very common, but possible. It is a bit hard to think upside down. There may be small ...
1 vote

### LM317 Voltage of 1.8v

Right values: R1 = 390 Ω R2 = 172 Ω Vout = 1.25 V (1 + 172 Ω / 390 Ω) = 1.8012 V Vout = ~1.8 V
1 vote

### How is voltage regulated on the output of this supply?

Voltage too high -> TL431 draws more current through opto Voltage too low -> TL431 draws less current through opto. The other half of the circuit uses that signal to regulate the output. This ...
1 vote

### AOZ2261 Buck Switching Regulator doesnt give reasonable Output

The IC can't work with VCC = 3.3V because UVLO threshold for rising VCC can be as high as 4.5V. Apply 5V to VCC pin. The datasheet recommends VCC = 5V which is the voltage that the IC is characterised ...
1 vote

### How to bypass simple zener diode voltage regulation at low volts?

Not a direct answer to your question, but for the system parameters you are targeting (input voltage range: 10-36V, output voltage:12V, output current < 500mA) there is a lot to be said for the ...
1 vote

### Load regulation of constant current source

You have two separate questions. First, the formula (with currents at miminum and maximum load resistances substituted for voltages) is applicable. This is only the effect of changing current with ...
1 vote

### Load regulation of constant current source

The wikipedia formula does apply, with the obvious change as you have a current output Load regulation % = $100 \frac{I_{min-load}-I_{max-load}}{I_{nom-load}}$ As R1 controls the output current, ...

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