Contents
Why is Schottky barrier diode used?
Schottky diodes are used for their low turn-on voltage, fast recovery time and low-loss energy at higher frequencies. These characteristics make Schottky diodes capable of rectifying a current by facilitating a quick transition from conducting to blocking state.
What is special about a Schottky diode?
Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. This lower forward voltage requirement allows higher switching speeds and better system efficiency.
How are Schottky diodes connected to the ground?
The Schottky diodes are connected to the ground and a 5 V system rail capable of sinking current. Without the Schottky diodes, there is a reference disturbance when the input exceeds the reference and ground by a diode drop. As can be seen, the reference disturbance is completely removed with the Schottky diodes.
What is the reverse leakage current of Schottky diodes?
Attention needs to be paid to the reverse leakage current of the Schottky diodes, as this may introduce distortion and nonlinearity during normal operation. This reverse leakage is very temperature dependent and is generally specified in the diode data sheet. A good option is the BAT54 series of Schottky diodes (2 μA max at 25°C, ~100 μA at 125°C).
When does the protection diode to ref turn on?
In Figure 1, if the amplifier was to rail toward the +15 V rail, the protection diode to REF will turn on and the amplifier will try to drag the REF node up.
How does the series resistor protect the ADC?
The series resistor after the Schottky diodes also helps limit the current into the ADC if the internal diodes turn on slightly. For extra protection, if the reference has little to no sink current capability, a Zener diode or clamp circuit could be used on the reference node to guarantee the reference voltage cannot be pulled too high.