Low-voltage power amplifiers KR1438UN2, KB1438UN2-4. Reference data
Encyclopedia of radio electronics and electrical engineering / Reference materials
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Audio frequency power amplifiers KR1438UN2 and KB1438UN2-4 are designed for use in portable AM/FM radio receivers, tape recorders and players, in two-way operational communication devices, in the output stages of television scanners, in the drive of low-power servomotors, in inverters, in ultrasonic devices and other equipment for various purposes.
The KR1438UN2 microcircuit is framed in a rectangular plastic case 2101.8-1 with flat stamped leads (Fig. 1); weight - no more than 1 g.
An analogue of the KR1438UN2 amplifier is LM386N (National Semiconductor Corp.).
Pinout of the KR1438UN chip: pin. 1 and 8 - pins for connecting an RC circuit for setting the required gain; pin. 2 - inverting input; pin. 3 - non-inverting input; pin. 4 - general; negative power output; pin. 5 - exit; pin. 6 - positive power output; pin. 7 - terminal for connecting the filter capacitor in the power supply circuit of the input stage.
Main technical characteristics at Tacr.Sr - 25 °С
- Supply voltage, V ...... 4 ... 12
- Quiescent current, mA, no more, at zero input voltage, supply voltage 6 V, load resistance 8 Ω and frequency 1 kHz...... 8
- Input bias current, nA, with pins 2 and 3 off and supply voltage 6 V......250
- Output power, mW, not less, with a load resistance of 8 Ohm, a harmonic coefficient of 10%, a frequency of 1 kHz for a supply voltage of 6 V ...... 250
- 9 V......500
- Voltage gain, dB, at a supply voltage of 6 V, a load resistance of 8 ohms, a frequency of 1 kHz with free outputs 1 and 8 ...... 26
- when turned on between pins 1 and 8 of a 10uF capacitor......46
- Bandwidth, kHz, at a supply voltage of 6 V, a load resistance of 8 ohms with free outputs 1 and 8 ...... 300
- when turned on between pins 1 and 8 of a 10uF capacitor......60
- Nonlinear distortion coefficient, %, at output power 125 mW, with free terminals 1 and 8......0,2
- Ripple smoothing coefficient, reduced to the output, dB, with free terminals 1 and 8 and a capacitor in the output circuit 7 with a capacity of 10 μF ...... 50
- Input resistance, kOhm, at a supply voltage of 6 V......50
- Thermal resistance crystal-case, °С/W......37
- Thermal resistance crystal-environment, °С/W......107
- Limit values
- The highest supply voltage, V ...... 15
- Maximum input voltage, V ...... ± 0,4
- Maximum power dissipation, mW......660
- The highest temperature of the crystal, ° С ...... 150
- Ambient temperature operating range, °С -20...+70
- Storage temperature, °С......-40...+125
Signals to the input of the amplifier should be applied relative to the common wire. The useful output signal is shifted by half the supply voltage. A typical amplifier switching circuit is shown in fig. 2. With the R2C1 circuit ratings shown in the diagram, the gain is 50.
The internal feedback circuit of the amplifier consists of three resistors connected in series - 150 Ohm, 1,35 kOhm and 15 kOhm. Pins 1 and 8 of the microcircuit are connected to the middle of these resistors.
If pins 1 and 8 are free, the gain is 20, and if a 10 uF capacitor is connected to them, the gain will reach a maximum value of 200. Intermediate gain values are obtained by connecting a resistor in series with the capacitor.
On fig. 3-6 show the main graphic characteristics of the KR1438UN2 amplifier. Rice. 3 shows the dependence on the supply voltage of the current consumed in the absence of an input signal, and fig. 4 - range of output voltage.
The frequency characteristics of the voltage gain (without capacitor C1-8 between pins 1 and 8 and with a 10 uF capacitor) and harmonic distortion are shown in fig. 5 and 6, respectively.
On fig. Figure 7 shows an example of an amplifier circuit with boost in the low-frequency portion of the passband (Figure 8).
On the KR1438UN2 chip, you can assemble simple generators. The generator circuit of a stabilized sinusoidal voltage 3H at a frequency of 1 kHz is shown in fig. 9, and in fig. 10 is a diagram of a rectangular pulse generator at the same frequency.
Author: A.Nefedov, Moscow
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