When the shutoff time is longer than the period of a high-frequency signal, a PIN diode with enough forward bias acts like a good conductor in both directions. That’s a common gotcha in making switching voltage converters work without blowing up.Ī PIN diode stores extra charge in the intrinsic region, which makes it stay conductive longer in the reverse direction. When you switch a diode from forward bias to reverse bias, it will conduct current the wrong way until it can sweep all the stored charge out of its depletion region. It makes them worse.ĭiode siwtches take advantage of a diode’s shutdown time, which is a function of the amount of charge stored in the depletion region. Minor correction: a PIN diode’s intrinsic layer doesn’t improve the shutoff characteristics. Posted in Parts Tagged PIN diode, RF, Switching circuit Post navigation See, the humble diode can be fun after all!
FET TRANSISTOR FOR MULTIPLE LEDS SERIES
Checkout how high voltage diodes are constructed, diodes detecting ionising radiation, and finally this great series about our new favourite two-terminal device. Of course, we’ve covered diodes many times from different angles, there is always something to learn.
While demonstrates this with a signal diode, as he explains, one would typically use a PIN diode, which has an extra intrinsic (undoped) region between the P and the N, allowing the device to fully turn off, reducing leakage significantly. And that makes a diode a DC controlled switch for AC signals. But if you take away the bias, by turning off the DC bias voltage source, the diode switches back to non-conducting, blocking the signal. Put another way, if you bias the diode into conduction, changes in the downstream voltage level result in changes in the current flowing through the diode, and the (smaller) AC signal gets through. Signals can be passed “the wrong way” through a diode by inducing small fluctuations in the current. So your DC signals can’t swim upstream, but the same isn’t true for AC. The trick is that diodes block current in one direction but allow it to flow in the other, denoted by the deliberately obvious symbol. Can you use a diode to switch a signal even if it has only two terminals? Of course you can, and it’s a tried and trusted technique very common in test equipment and circuits that handle RF signals. Typical devices that spring to mind are bipolar transistors, triacs and and ye olde triode valve. Many hardware people around these parts will be familiar with devices used as switches, using at least three-terminals to effect this, an input, an output and a gate.
0 kommentar(er)
