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2N Datasheet pdf – NPN/PNP PLASTIC POWER TRANSISTORS – Boca Semiconductor Corporation
Today’s complex electronic systems are requiring greater datasheeg performance, higher efficiency and lower parts count. Present integrated circuit and power package technology has produced IC volta- ge regulators which can ease the task of regulated power supply design, provide the performance required and remain cost effective.
Available in 2n489 growing variety, Motorola offers a wide range of regulator products from fixed and adjustable voltage types to special-function and switching regu- lator control ICs.
This manual describes Motorola’s voltage regulator products and provides information on applying these products. Basic Linear regulator theory and switching regulator topologies has been daasheet along with practical design examples. Other relevant topics include: A Motorola regulator selector guide along with data sheets and an industry cross-reference are also contained in this handbook. A transistor and rectifier selec- tor guide for switching regulators of various configurations and power levels is provided in Appendix A and B.
This information has been carefully checked and is believed to be entirely reliable. Hovewer, no responsibility is assumed for inaccuracies. Motorola reserves the right to make changes to any products herein to improve reliability, function or design. Motorola does not assume any liability arising out of the application or use of any product or circuit herein described.
No license is conveyed under patent rights in any form. When this doc- ument contains information on a new product, specifications herein are subject to change without notice.
The Future for Switching Regulators Section Package Outline Dimensions Section It consists of a stable reference, whose output voltage is Vref, and a high gain error amplifier. The output voltage, Vo, is equal to, or a multiple of, Vref. The regulator will tend to keep Vo constant by sensing any changes in Vo and trying to return it to its original value.
Therefore, the ideal voltage regulator could be considered a voltage source with a constant output voltage. However, in practice the IC regulator is better represented by the model shown in Figure In this figure, the regulator is modeled as a voltage source with a positive output impedance, Zo. The value of the voltage source, V, is not constant; instead, it varies with changes in supply voltage, Vcc, and with changes in IC junction temperature, T, induced by changes in ambient temperature and power dissipation.
Also, the regulator output voltage, Vo, is affected by the voltage drop across Zo, caused by the output current, Io. In the following text, the reference and amplifier sections will be described, and their contributions to the changes in the output voltage analyzed. It consists of a resistor and a zener diode. The zener voltage, Vz, is used as the reference voltage.
In order to determine Vz, consider Figure l-3b.
The zener diode, VR1of Figure l-3a has been replaced with its equivalent circuit model and the value of Vz is therefore given by at a constant junction temperature: The value of the zener current is largely independent of Vcc and is given by: The reference voltage about 7 V of this configuration is therefore largely inde- pendent of supply voltage variations.
This configuration has the additional benefit of better temperature stability than that of a simple resistor- zener reference. Referring back to Figure l-3a, it can be seen that the reference voltage temperature stability is equal to that of the zener diode, VR 1. A variation this large is usually unacceptable. However, the circuit of Figure does not have this drawback. Here the positive 2.
This results in a reference voltage with 2m6489 stable temperature characteristics. Constant Current – Zener Reference The Bandgap Reference Although very stable, the circuit of Figure 1 -4 does have a disadvantage in that it requires a supply voltage of 9 volts or more. Another type of stable reference which requires only a few volts to operate was described by Widlar 1 and is shown in Figure In this circuit Vref is dtasheet by: Figure shows a typical diffe- rential error amplifier in a voltage regulator configuration.
With a constant supply voltage, Vcc, and junction temperature, the output voltage is given by: Note also that if Avol is not infinite, with constant output current a non-varying output loadthe output voltage can still be “tweaked in” by varying Ri and R2, even though Vo will not exactly equal that given by equation 1 1.
Assuming a stable reference and a finite value of Avol, inaccuracy of the output voltage can be traced to the following amplifier characteristics: Amplifier input offset voltage drift — The input transistors of integrated circuit amplifiers are usually not perfectly matched. As in operational amplifiers, this is expressed in terms of an input offset voltage, Vio. Closer matching of the internal amplifier input transistors, minimizes this effect, as does selecting a feedback ratio, j8, to be close to unity.
Amplifier power supply sensitivity — Changes in regulator output voltage due to power supply voltage variations can be attributed to two amplifier performance parameters: In modern integrated circuit regulator amplifiers, the utilization of constant current sources gives such large values of PSRR that this effect on Vo can usually be neglected.
However, supply voltage changes can affect the output voltage since these changes appear as common mode voltage changes, and they are best measured by the CMRR. The definition of common mode voltage, Vcm, illustrated by Figure l-7a, is: In fact, Vcm does influence the amplifier output voltage. The latter figure is the same configuration as Figurewith amplifier input offset voltage and output impedance deleted for clarity and common-mode voltage effects added.
The output voltage of this configuration is given by: Amplifier Output Impedance — Referring back to equation 9it can be seen that the equivalent regulator output impedance, Zo, is given by: A simple way of lowering the effective value of Zol is to make an impedance transformation with an emitter follower, as shown in Figure These are shown in Table along with procedures which minimize their effects.
However, this method presents a basic problem to the regulator designer. If the configuration of Figure is used, the output voltage cannot be adjusted to a value other than Vref. The solution is to utilize a different regulator configuration known as the “regulator within a regulator approach.
Constant current-zener method 2. Bandgap reference Ti 1. TC compensated zener method Amplifier Vcc 1. High CMRR amplifier 2. High Avol amplifier 3. Low Vio drift amplifier 2. Low Zol amplifier 2. Additional emitter follower output 4. SC-3, Number 4, Dec. Each has its own particular charac- teristics and best uses, and selection depends on the designer’s needs and trade-offs in performance and cost.
Positive Versus Negative Regulators. In most cases, a positive regulator is used to regulate positive voltages and a negative regulator negative voltages.
However, depending on the system’s ground- ing requirements, each regulator type may be used to regulate the “opposite” voltage.
Figures 2- la and 2- lb show the regulators used in the conventional and obvious mode. Note that the ground reference for each indicated by the heavy line is continuous. Several positive regulators could be used with the same input supply to deliver several voltages with common grounds; negative regulators may be utilized in a similar manner.
If no other common supplies or system components operate off the input supply to the regulator, the circuits of Figures 2- 1 c and 2- 1 d may be used to regulate positive voltages with a negative regulator and vice versa. In these configurations, the input supply is essentially floated, i. There are methods of utilizing positive regulators to obtain negative output voltages without sacrificing ground bus continuity; however, 26n489 methods are only possible at the expense of increased circuit complexity and cost.
An example of this technique is shown in Section 3. Three Terminal, Fixed Output Regulators These regulators offer the designer a simple, inexpensive way to obtain a source of regulated voltage. They are available in a variety of positive or negative output voltages and current ranges. The advantages of these regulators are: Methods for obtaining ad- justable outputs are shown in Section 3. Methods for obtaining greater output currents are shown in Section 3. Regulator Configurations 3.
Three Terminal, Adjustable Output Regulators Like the datssheet terminal fixed regulators, the three terminal adjustable reg- ulators are easy and inexpensive to use. These devices provide added flexibility with output voltage adjustable over a wide range, from 1. A 2n64889 of current ranges from mA to 3. Tracking Regulators Often a regulated source of symmetrical positive and negative voltage is required for supplying op amps, etc. In these cases, a tracking regulator is required.
In addition to supplying regulated positive and negative output voltages, the tracking regulator assures that these voltages are balanced; in other words, the midpoint of the positive and negative output voltages is at ground potential.
This function can be implemented using a positive output regulator together with an op amp or negative output regulator. However, this method results in the use of two IC packages and a multitude of external components.
To minimize component count, an IC is offered which dayasheet this function in a single package: The output voltage of this regulator can be any magnitude and is limited only by the capabilities of an external transistor. However, an additional floating low voltage input supply is required.
To provide higher currents than are available from monolithic technologiesan IC regulator will often be used as a driver to a boost transistor.