File: /var/www/html/simulink/circuit/mosfet-beta.html
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{display:none !important;}</style></head><body><h1>MOSFET Beta</h1>
We use a parameter called "beta" to describe the behavior of a MOSFET. The default value is small (20m), which is appropriate for a signal MOSFET. To simulate
a power MOSFET, use a larger value like 80.
<p>
In the saturation region, I<sub>ds</sub> = beta * (V<sub>gs</sub> - V<sub>t</sub>)<sup>2</sup>/2.
<p>
This worksheet will calculate the value of beta for a particular MOSFET, given Rds(on).
<p>
<script>
function units(x) {
x = x.trim();
if (x.match(/m$/)) {
x = x.replace(/m$/, "");
return .001 * x;
}
// don't think we need this but you never know
if (x.match(/u$/)) {
x = x.replace(/u$/, "");
return 1e-6 * x;
}
return x;
}
function calc() {
var rds = units(document.getElementById('rds').value);
var vgs = units(document.getElementById('vgs').value);
var vt = units(document.getElementById('vt').value);
var beta = Math.abs(1/(rds*(vgs-vt)));
document.getElementById('result').innerHTML = "beta = " + beta;
}
</script>
<form action="/action_page.php">
R<sub>DS</sub>(on) (Ω) (use typical value): <input type="text" id="rds" oninput="calc()"><br>
V<sub>GS</sub> where measured (V): <input type="text" id="vgs" oninput="calc()"><br>
Threshold (V) (use typical value): <input type="text" id="vt" oninput="calc()"><br>
</form>
<div id="result">
</div>
</body></html>