Small Signal Diode – Working & Its Applications

While Talking about Small Signal diodes first of all we need to understand what is a small signal. Then after studying how the Small Signal Diode works and what are its applications we also get to understand how it is different from other diodes.

What is a Small Signal?

A small signal is referred to which has a small amplitude and varies in time. A small signal gives a linear characteristics curve over a limited range of voltage and current since many devices are non-linear over their whole operating range.

A small Signal Diode is a small electronic device that has an essential role at high frequency and very low current applications such as radios, televisions, etc. They generally have smaller junction areas giving the junction-less capacitance making them more useful at higher frequencies.
The symbol for Small Signal Diode is the same as that is for any other signal diode or a typical P-N diode as shown below

Now to understand the working of a small signal diode we need to take an overview of its physical structure which is shown below in the figure

The construction of a small signal diode includes two layers P-type and N-type. The N-type layer is separated into two regions like N- and N+ where one region (N-) is near the p-type material that is lightly doped & another layer is near the heavily doped cathode contact. A silicon oxide insulating layer or glass layer is imposed on the whole structure to guard the diode against oxidation. So, the construction will make the diode more consistent which results in better reliability of its parameter.
The diode conducts current when the positive supply is applied to the anode and the negative supply is applied to the cathode of the diode. If the voltage is given in the reverse direction then the diode blocks any current. Ideally, this diode must block a negative signal completely.

They are commonly used in electronic circuits within radios, televisions & digital logic circuits, etc.
These diodes are also used in a variety of signal processing applications.
The small signal diodes are also used in digital devices for clocking functions and also avoid the reverse signal from harming the microcontroller.
These are used in clipping and switching applications where small duration pulse signals are normally clipped off.
Signal diodes are frequently used for clipping AC signals. One or more signal diodes can be used to clip an input signal.