Switching Regulator Circuit Using LM1758 A

This is a circuit for a switching regulator which can easily be set up for such dc-to-dc voltage .conversion circuits as the buck, boost, and inverting configurations. This is the figure of the circuit;

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 up to 750 m A and has output pins for its collector and emitter to promote design flexibility. An external current limit terminal may be referenced to either the ground or the Vin terminal, depending upon the application. In addition, the LM 1578 A has an on board oscillator, which sets the switching frequency with a single external capacitor from < 1 Hz to 100 kHz (typical). It operates from supply voltages of 2 V to 40 V. It is provided with current limit and thermal shutdown. Duty cycle up to 90 %.

Differential Analog Switch Circuit

This circuit is design circuit for a differential analog circuit switches. The FM1208 monolithic dual differential multiplexer used in applications where the RDS (ON) must be the same match. Since RDS (ON) for monolithic dual tracks at better than 1% of the broad temperature range (-25 to 125 C) is making an unusual choice, but ideal for a multiplexer accurate. This greatly reduces the close tracking errors due to common mode signals. OP-Amp is  used LM107. This is the figure of the circuit;

Circuit source: National semiconductor Application

Low Drop Out (LDO) Voltage Regulator Circuit Using Discrete Semiconductor

There are several integrated circuit chips designed specially for LDO (low drop out) voltage regulator. Building LDO using standard op-amp and discrete components can be an alternative. This is the figure of the circuit;

To design the circuit, this is the guideline to change the value of components;
·    D1 is chosen for the best performance, the sharper the on-off transition curve the better. Some people say that 5,6V Zener diode has better voltage regulation than other voltage. But you can actually use any voltage below the expected minimum output voltage. The output voltage will be Vd(R4+R3)/R3, with Vd is the voltage of the Zener diode D1.
·    R1 is selected so the exact voltage of D1 will have minimum drift over the input supply range variation.  Look at the D1 datasheet. R1 is usually not critical, and you can use larger value to save the current loss.
·    R3 and R4 uses to set the expected output voltage, and are chosen as large as possible to conserve the current loss, but should be much smaller than the op-amp’s input impedance.
·    Q1 is chosen for the lowest Vce drops for the best performance, the higher gain (hFe), and the collector current must be capable to handle the expected maximum load current.
·    Q2 must have low drop Vce if the regulator is expected to regulate low voltage source, but not so critical if the input supply voltage is high.
·    R2 can be selected to make sure that Q2 is always “on” even when the regulator is unloaded.  Just remember that the voltage across R2 is same with Vbe of Q1, you can set the value of R2 to set the current Ice of Q2 at the best  of Q2′s Ibe/Ice curve.
·    Select The op-amp A1 for the best high gain, highest input impedance. The most important character for A1 is that the output swing should be capable to go down below  Q2 Vbe turn-on point.

Digitally Controlled Phase Shifter Circuit

This is a circuit for the circuit implementation of phase shifter circuit is well suited to using digital potentiometer to control the resistive control element of  the phase shifter. This is the figure of the circuit; 

The phase at a given frequency is now under control of a digital signal using this circuit which is optimized for phase-shifting over the audio range. By using a single digital control line, the DS1669 used here can have its wiper position set to cause the wiper position increment upon each low-going pulse, until it reaches the upper end of the pot, when it will reverse direction and decrement.To cause the phase constantly sweep (an effect commonly used in popular recordings today), we can supply a clock to this digital control input. The digital potentiometer is biased at 1/2 VCC since this is a single supply circuit. [Circuit schematic source: maxim-ic application notes].

Low Cost Buffered Voltage Reference Circuit

This is design circuit for a low-cost voltage reference circuit.  Its main component is a general-purpose operational amplifier, the 741, configured to output a buffered fixed reference voltage for use by other IC's or circuits, such as an Analog-to-Digital Converter (ADC). This is the figure of the circuit;

The reference circuit above is designed to output 5 volts, and employs an AD589 as the 741's own reference.  The AD589 is a low-cost, temperature-compensated bandgap voltage reference that provides a constant output of 1.23 V.  Thus, the voltage at both inputs of the 741 is 1.23 V, which is also the voltage at the junction of the 1K and 3K resistors connected to the inverting input. This forces the 741 to output a steady voltage of approximately 5V (1.23V x 4K/1K = 4.92V). 

Low Voltage AC Voltmeter Circuit

This is a design circuit for AC voltmeter for measuring low AC voltages. The main component of this circuit is an operational amplifier (such as the 741 or 351), configured as an amplifier whose feedback circuit is a diode bridge full-wave rectifier. This is the figure of the circuit;

The op amp's output current in both the positive and negative cycles flows through it in only one direction.  In effect, the average of the op amp's output ac current io, which passes through the ammeter as a dc current, is measured by the ammeter. With full wave rectification, the meter current is given by: io = 0.9 Vin/R, or Vin = 1.1 ioR.  Note that this project requires calibration so that the meter will register the rms value of the input voltage Vin.
 

Discrete Voltage Regulator Circuit

It is still possible to build circuits without IC’s and still achieve a high level of performance while integrated circuits have become a staple of all modern circuit designs. A high performance 5 volt voltage regulator built using discrete components. This is the figure of the circuit;


This circuit is not need an IC and only need to substitution a 1N4001 in lieu of a zener diode. The regulator output voltage is varies by mere 4 %. It’s also has current limiting at 1.5 amps along with short circuit protection. This circuit closely matches the performance of the 7805 5 volt regulator IC with the exception of thermal shutdown.

We can adjust this circuit as a 12 volt regulator by adjusting R4 to the desired output voltage. The input voltage must be inside the range, 18V-25. Increase resistor R1 to 2.2K for best performance if you plan to use this circuit as a 12 volt regulator. The limit of the circuit still at 1.5 amps regardless of the output voltage setting. All resistors used in this circuit are ¼ watt except for R2 which must be at least a 2 watt type or larger. In this circuit, Almost any general purpose NPN transistor can be substituted for the 2N3904 transistors used. For Q3 we can used any similar TO220 type NPN switching transistor. A zener diode can be substituted for D1 but the voltage should be at least 2 volts lower than the desired output voltage if we desired. It’s require to use of zener diode to make resistors R3 and R4 decreased accordingly.

[Circuit source: Radio Amateur Society of Norwich]

Low Drop-Out Constant Current and Constant Voltage 2-Cell Charger

This circuit is design for Li-Ion battery charger that features a dropout voltage of less than one volt. This charger is a constant-current and constant-voltage charger. Here’s the figure of the circuit.


The operation in the circuit is constant-current mode at the beginning of the charge cycle and switches over to a constant-voltage mode near the end of the charging cycle. The circuit consists of two basic feedback loops. The first loop controls the constant charge current delivered to the battery, and the second determines the final voltage across the battery. With a discharged battery connected to the charger, (battery voltage is less than 8.4V) the circuit begins the charge cycle with a constant charge current. The value of this current is set by using the reference section of the LM10C to force 200 mV across R7 thus causing approximately 100 μA of emitter current to flow through Q1, and approximately 1 mA of emitter current to flow through Q2. The collector current of Q1 is also approximately 100 μA, and this current is flows through R2 developing 50 mV across it. This 50 mV is used as a reference to develop the constant charge current through the current sense resistor R1. [Circuit’s source: National Semiconductor Notes].

1,5A High Efficiency Synchronous Switching Regulator Evaluation Board

This is a design for evaluation circuit. This circuit is based on LM2651. This is the figure of the circuit.


The evaluation board is designed to supply 3.3V at 15 mA up to 1.5A. The input voltage range is 4V to 14V. PCB layout is critical to reduce noise and ensure specified performance for any power supply design. To minimize the parasitic inductance in the loop of input capacitors and the internal MOSFETs, connect the capacitors to VIN and PGND pins with short and wide traces. This is important because the rapidly switching current, together with wiring inductance can generate large voltage spikes that may cause noise problems. The feedback trace from the output to the feedback pin should be wide, short and kept away from the flux field of the inductor.

1,5A High Efficiency Synchronous Switching Regulator Evaluation

This is a switching regulator circuit that is work using regulator IC LM2651. This circuit provides high efficiency power conversion over a 100:1 load range (1.5A to 15mA). This is the figure of the circuit.


Synchronous rectification and 75 mΩ internal switches provide up to 97% efficiency. At light loads, the LM2651 enters a low power hysteretic or sleep mode to keep the efficiency high. In many applications, the efficiency still exceeds 80% at 15 mA load. A shutdown pin is available to disable the LM2651 and reduce the supply current to 7 μA. The IC contains patented current sensing circuitry for current mode control. This feature eliminates the external current sensing required by other current mode DC to DC converters. The IC has a 300 KHz fixed frequency internal oscillator. The high oscillator frequency allows the use of extremely small, low profile components.

Switch Mode 3.3A 10A Regulator

This switch mode regulator circuit has higher current output than our previous switch mode regulator, but it uses same controller IC. Up to 10A can be served by this switch mode regulator. The output of this regulator circuit is regulated at 3.3 volt, and the input range is 4-9 volt. This is the figure of the circuit.


The SHDN pin can be pulled high (CMOS level) to shut down the operation of the circuit shut the current down to 50uA or less. This SHDN pin must not left unconnected, should be connected to ground for normal operation or connected to 1.5V or more potential to shut down the operation, you can do this by hard wiring, switch, or CMOS logic. To optimize efficiency, this switch mode regulator automatically switches between two modes of operation, burst and continuous, and this automatic setting require the BINH pin to be grounded. When you want the burst mode to be disabled, you should connect this BINH pin to the voltage input supply. [Circuit's source: Linear Technology, Inc Application Notes]

Variable Voltage Regulator Circuit Using LM317

This is a design for voltage regulator that can adjust from 1.25 to 37 volts. This circuit is a simple design. The voltage regulator is control by op amp LM317. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof. This is the figure of the circuit.


Output voltage is set by two resistors R1 and R2 connected as shown below. The voltage across R1 is a constant 1.25 volts and the adjustment terminal current is less than 100uA. The output voltage can be closely approximated from Vout=1.25 * (1+(R2/R1)) which ignores the adjustment terminal current ``but will be close if the current through R1 and R2 is many times greater. A minimum load of about 10mA is required, so the value for R1 can be selected to drop 1.25 volts at 10mA or 120 ohms. Something less than 120 ohms can be used to insure the minimum current is greater than 10mA. The example below shows a LM317 used as 13.6 volt regulator. The 988 ohm resistor for R2 can be obtained with a standard 910 and 75 ohm in series. When power is shut off to the regulator the output voltage should fall faster than the input.

Boosting Regulator Current Circuit

This is design of a pass transistor used to increase the current output of a voltage regulator IC. The circuit is design by Andy Collinson. This circuit is control by regulator IC. The IC that using in the circuit is 78xx series. This is the figure of the circuit.


The operation of the circuit is description by a power transistor is used to supply extra current to the load the regulator, maintaining a constant voltage. The currents up to 650mA will flow through the regulator, above this value and the power transistor will start to conduct, supplying the extra current to the load. This should be on an adequate heat sink as it is likely to get rather hot. Suppose you use a 12v regulator, 7812.