Electronic Circuits and Diagram-Electronics Projects and Design

The National Semiconductor LM 1578 A is a switching regulator which can easily be set up for such dc-to-dc voltage .conversion circuits as the buck, boost, and inverting configurations. The LM 1578 A features a unique comparator input stage which not only has separate pins for both the inverting and non-inverting inputs, but also provides an internal 1.0 V reference to each input, thereby simplifying circuit design and PC board layout. The output can switch upto 750 m A and has output pins for its collector and emitter to promote design flexibility. An external current limit terminal may be referenced…

Switching Regulators Using LM 2575 and LM 2577 Switching regu­lators are available is different circuit configurations in­cluding the flyback, feed-forward, push-pull, and non-iso­lated single-ended or single-polarity types. Also, the switching regulators can operate in any of three modes – step-down, step-up, or polarity inverting. LM 2575 series of regulators developed by National Semiconductor are monolithic IC’s that provide the active functions for step-down (back) switching regulator, capable of driving a1A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V and an adjustable output version. Requiring a minimum number of…

Switching Voltage Regulators All of the voltage regulators we have discussed so far are series regulators, also sometimes called the linear regulators because the pass transistor used in such a regulator operates in the active region. Series regulators are very popular and meet many of our needs. The main drawback of these regulators is the power dissipation in the pass transistor. As already mentioned above, the transistor used in these regulators is operated in its linear mode (active region). In essence, it is being used as a class A power amplifier. Conse­quently, it is not extremely efficient, and a great-deal…

Dual Power Supply using LM 320 and LM 340 Many discrete and ICs need bipolar (dual or ± V) supplies. This can be easily accomplished with two three-terminal regulators, as illustrated in figure. Opposite-phase ac is provided by the transformer’s secondary and a grounded center tap. The single full-wave bridge converts these into positive and negative dc voltages (with respect to the grounded center tap). Filtering (with respect to ground) is provided by capacitors C1 and C2. The LM 340 provides regulation of the positive voltage, while the LM 320 regulates the negative voltage. It is very important to mention…

Figure shows the basic circuit of an IC 723 voltage regulator. This IC has a voltage reference source, an error amplifier, a series pass transistor, and a current limiting tran­sistor all contained in one small package. The device can be connected to operate as a positive or negative voltage regulator with an output voltage ranging from 2 V to 37 V, and output current levels upto 150 m A. The maximum supply voltage is 40 V, and the line and load regulations are each specified as 0.01%. Figure shows an IC 723 connected to operate as a positive voltage regulator….

Three terminal voltage regulators This series is typical of the three-terminal voltage regulators. The block diagram is shown in figure. The built-in reference voltage VREF drives the non-inverting input of an op-amp. The operational amplifier consists of several stages of volt­age gain. Because of the high gain of the op-amp, the error voltage between the two input terminals of the op-amp approaches zero. So the inverting input voltage is approximately equal to VREF. This means that current flowing through the potential divider I = VREF / R’2 Incidentally, the prime attached to R’2 indicates that this resistor is inside the…

Adjustable Voltage Regulators Some­times variable voltage is required and under such a situation adjustable voltage regulator is used. A number of IC regulators, like LM 317, LM 338, and LM 350, are adjustable regulators. They have maximum load currents from 0.10 to 1.5 A. For example, the LM317 is a three terminal positive voltage regulator, which can be oper­ated with the output voltage regulated at any setting over the range of 1.2 V to 57 V. Figure illustrates how the regulated output voltage of an LM317 can be set. Resistors Rx and R2 set the output to any desired voltage…

IC voltage regulators are versatile and relatively inexpensive and are available with fea­tures such as a programmable output, current-voltage boosting, internal short-circuit cur­rent limiting, thermal shutdown, and floating operation for high voltage applications-Voltage regulators comprise a class of widely employed ICs. Regulator IC units contain the circuitry for reference source, comparator amplifier, control device, and overload pro­tection all in a single IC. Although the internal construction of IC is somewhat different from that explained in case of discrete voltage regulator circuits, the external operation is almost the same. A power supply can be built using a transformer connected to the…

6 Volt Regulator using IC 7806 Description. Here is the elementary 6V 1A power supply circuit using 7806 IC. The 7806 three-terminal positive voltage regulator is available in the TO-220/D-PAK package making them useful in a wide range of applications. 7806  employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If proper heat sinking is provided, it can deliver over 1 ampere output current. Voltage Regulator Circuit Diagram with Parts List . Pin out of 7806 Notes . If 2A bridge is not available make one with four 1N 4007 diodes. Fit a…

Adjustable/Variable Voltage Regulator using LM 117 Description This is the circuit diagram of a 1.2 V to 25 Volts adjustable voltage regulator using IC LM 117 IC.The LM117 series of adjustable 3-terminal positive voltage regulators are able to provide in excess of 0.5A over a 1.2V to 37V output range. They are very easy to handle and require only two external resistors to set the output voltage. This power supply is able to deliver a maximum of 0.5 A current.The circuit is easy to assemble and provides great results.Resistances R1 and R2 are used for voltage adjustment.Vary pot R2 to…