Editing Basic Voltage Regulators
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− | Standard through-hole regulators typically come in TO-220 packages for low current, and TO-3P packages for currents above 1.5A. Heatsinking is typically easy, however note that regulators may or may not have a 'hot' tab, with the output electrically connected to the heatsinking tab, particularly in the case of older TO-3 metal can regulators. Electrical isolation is | + | Standard through-hole regulators typically come in TO-220 packages for low current, and TO-3P packages for currents above 1.5A. Heatsinking is typically easy, however note that regulators may or may not have a 'hot' tab, with the output electrically connected to the heatsinking tab, particularly in the case of older TO-3 metal can regulators. Electrical isolation is required for multiple regulators on the same heatsink, a LM317 adjacent to a LM337 on a heatsink with the output tabs connected are the equivalent of a short, causing high current and failure.<br><br> |
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As the LM7XXX series regulators are mass produced and relatively inexpensive, 200-500mV of noise can be expected. Manufacturer datasheets typically recommend a 10-100uF decoupling capacitor be placed between output and ground to smooth the output, and give voltages clean enough for TTL operation amongst other applications.<br><br> | As the LM7XXX series regulators are mass produced and relatively inexpensive, 200-500mV of noise can be expected. Manufacturer datasheets typically recommend a 10-100uF decoupling capacitor be placed between output and ground to smooth the output, and give voltages clean enough for TTL operation amongst other applications.<br><br> | ||
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Regulator pinouts are as follows:<br> | Regulator pinouts are as follows:<br> | ||
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− | <tr><td></td> <td>Pin 1</td> <td>Pin 2 | + | <tr><td></td> <td>Pin 1</td> <td>Pin 2</td> <td>Pin 3</td></tr> |
<tr><td>LM78XX Fixed</td> <td>Input</td> <td>Gnd</td> <td>Output</td></tr> | <tr><td>LM78XX Fixed</td> <td>Input</td> <td>Gnd</td> <td>Output</td></tr> | ||
<tr><td>LM79XX Fixed</td> <td>Gnd</td> <td>Input</td> <td>Output</td></tr> | <tr><td>LM79XX Fixed</td> <td>Gnd</td> <td>Input</td> <td>Output</td></tr> |