We introduced positive voltage regulator circuit in previous post. This is a Negative Voltage Regulator Circuit. Some circuits need the dual power supply (Ex: +12V / 0V / -12V). There we need fixed negative power supply, especially for digital electronic circuits. This voltage regulator circuit designed using Fixed Negative Voltage Regulator IC. You can use 79xx series regulator ICs (Ex: 7905, 7908) for this circuit. The supply
voltage is between -8V to -30V and you need to decide output voltage
according to the supply voltage of your circuit. The supply voltage of
regulator IC must be greater than -2V or more, than the output voltage of
its. By last two numbers of regulator IC indicates the output voltage of its. You can select regulator IC that you need, by using this table.
| IC No. | Voltage | |
|---|---|---|
| 7905 | → | -5V |
| 7906 | → | -6V |
| 7908 | → | -8V |
| 7909 | → | -9V |
| 7910 | → | -10V |
| 7912 | → | -12V |
| 7915 | → | -15V |
| 7918 | → | -18V |
| 7924 | → | -24V |
Also, this ICs similar to 78xx series and comes to market with-having various output power like 500 milli ampere (Ex:79Mxx), 5 ampere (Ex:79Hxx), etc. Sometimes, those are rare to find in local market. This table helps to find the maximum output current its.
| IC No. | Output Current | Package | ||
|---|---|---|---|---|
| 79Lxx (Ex: 79L05) | → | 100mA | → | To92 |
| 79Mxx (Ex: 79M05) | → | 500mA | → | To220 |
| 79xx (Ex: 7905) | → | 1A | → | To220 |
| 79Sxx (Ex: 79S05) | → | 2A | → | To220 |
| 79Txx (Ex: 79T05) | → | 3A | → | To220 |
| 79Hxx (Ex: 79H05) | → | 5A | → | To3 |
If maximum output current is grater than 100mA, then install proper heat-sink to regulator IC.
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Components:
IC – LM79XX Series Regulator IC
C1 - 2200μf / 50V
C2, C3 – 0.01μf (103) Ceramic
Input – (-8V) to (-30V) DC Voltage
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Mar 2, 2011
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