LM2878 Dual 5 Watt Power Audio Amplifier General Description Features The LM2878 is a high voltage stereo power amplifier designed to deliver 5W/channel continuous into 8X loads. The amplifier is ideal for use with low regulation power supplies due to the absolute maximum rating of 35V and its superior power supply rejection. The LM2878 is designed to operate with a low number of external components, and still provide flexibility for use in stereo phonographs, tape recorders, and AM-FM stereo receivers. The flexibility of the LM2878 allows it to be used as a power operational amplifier, power comparator or servo amplifier. The LM2878 is internally compensated for all gains greater than 10, and comes in an 11-lead single-in-line package (SIP). The package has been redesigned, resulting in the slightly degraded thermal characteristics shown in the figure Device Dissipation vs Ambient Temperature. Y Y Y Y Y Y Y Wide operating range 6V – 32V 5W/channel output 60 dB ripple rejection, output referred 70 dB channel separation, output referred Low crossover distortion AC short circuit protected Internal thermal shutdown Applications Y Y Y Y Stereo phonographs AM-FM radio receivers Power op amp, power comparator Servo amplifiers Typical Applications Frequency Response of Bass Tone Control TL/H/7934 – 2 TL/H/7934 – 1 FIGURE 1. Stereo Phonograph Amplifier with Bass Tone Control C1995 National Semiconductor Corporation TL/H/7934 RRD-B30M115/Printed in U. S. A. LM2878 Dual 5 Watt Power Audio Amplifier December 1994 Absolute Maximum Ratings Storage Temperature If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage Input Voltage (Note 1) 35V g 0.7V Operating Temperature (Note 2) 0§ C to a 70§ C b 65§ C to a 150§ C Junction Temperature a 150§ C Lead Temperature (Soldering, 10 sec.) Thermal Resistance iJC iJA a 260§ C 10§ C/W 55§ C/W Electrical Characteristics VS e 22V, TTAB e 25§ C, RL e 8X, AV e 50 (34 dB) unless otherwise specified. Parameter Total Supply Current Conditions Min PO e 0W Operating Supply Voltage Typ Max Units 10 50 mA 6 Output Power/Channel f e 1 kHz, THD e 10%, TTAB e 25§ C f e 1 kHz, THD e 10%, VS e 12V Distortion 5 32 V 5.5 1.3 W W f e 1 kHz, RL e 8X PO e 50 mW 0.20 % PO e 0.5W 0.15 % PO e 2W 0.14 % Output Swing RL e 8X VS b 6V Vp-p Channel Separation CBYPASS e 50 mF, CIN e 0.1 mF f e 1 kHz, Output Referred VO e 4 Vrms b 50 b 70 dB CBYPASS e 50 mF, CIN e 0.1 mF f e 120 Hz, Output Referred Vripple e 1 Vrms b 50 b 60 dB b 60 dB g 13.5 V PSRR Power Supply Rejection Ratio PSRR Negative Supply Measured at DC, Input Referred Common-Mode Range Split Supplies g 15V, Pin 1 Tied to Pin 11 Input Offset Voltage Noise Open Loop Gain 10 mV Equivalent Input Noise RS e 0, CIN e 0.1 mF BW e 20 b 20 kHz 2.5 mV CCIR # ARM 3.0 mV Output Noise Wideband RS e 0, CIN e 0.1 mF, AV e 200 0.8 mV 70 dB RS e 51X, f e 1 kHz, RL e 8X Input Bias Current Input Impedance Open Loop DC Output Voltage VS e 22V 10 Slew Rate Power Bandwidth 3 dB Bandwidth at 2.5W Current Limit 100 nA 4 MX 11 12 V 2 V/mS 65 kHz 1.5 A Note 1: g 0.7V applies to audio applications; for extended range, see Application Hints. Note 2: For operation at ambient temperature greater than 25§ C, the LM2878 must be derated based on a maximum 150§ C junction temperature using a thermal resistance which depends upon device mounting techniques. 2 Typical Performance Characteristics Device Dissipation vs Ambient Temperature Power Supply Rejection Ratio (Referred to the Output) vs Frequency Power Supply Rejection Ratio (Referred to the Output) vs Frequency Power Supply Rejection Ratio (Referred to the Output) vs Supply Voltage Channel Separation (Referred to the Output) vs Frequency Total Harmonic Distortion vs Frequency Total Harmonic Distortion vs Frequency Total Harmonic Distortion vs Power Out Open Loop Gain vs Frequency Power Output/Channel vs Supply Voltage Power Dissipation vs Power Out TL/H/7934 – 3 3 TL/H/7934 – 4 Equivalent Schematic Diagram 4 Connection Diagram Application Hints The LM2878 is an improved LM378 in typical audio applications. In the LM2878, the internal voltage regulator for the input stage is generated from the voltage on pin 1. Normally, the input common-mode range is within g 0.7V of this pin 1 voltage. Nevertheless the common-mode range can be increased by externally forcing the voltage on pin 1. One way to do this is to short pin 1 to the positive supply, pin 11. The only special care required with the LM2878 is to limit the maximum input differential voltage to g 7V. If this differential voltage is exceeded, the input characteristics may change. Single-In-Line Package Figure 2 shows a power op amp application with AV e 1. The 100k and 10k resistors set a noise gain of 10 and are dictated by amplifier stability. The 10k resistor is bootstrapped by the feedback so the input resistance is dominated by the 1 MX resistor. TL/H/7934 – 5 Top View *Pin 6 must be connected to GND. Order Number LM2878P See NS Package Number P11A TL/H/7934 – 6 FIGURE 2. Operational Power Amplifier, AV e 1 5 External Components (Figure 3) 6. C4, C8 1. R2, R5, R7, R10 Sets voltage gain AV e 1 a R2/R5 for one channel and AV e 1 a R10/R7 for the other channel. 2. R4, R8 Resistors set input impedance and supply bias current for the positive input. 3. RO Works with CO to stabilize output stage. Improves power supply rejection (see Typical Performance Characteristics). Stabilizes amplifier, may need to be larger depending on power supply filtering. 4. C1 5. C11 Input coupling capacitor. Pins 4 and 8 are at a DC potential of VS/2. Low frequency pole set by: fL e 7. C5, C7 1 2qR4C4 Feedback capacitors. Ensure unity gain at DC. Also low frequency pole at: fL e 8. CO 9. C2, C10 1 2qR5C5 Works with RO to stabilize output stage. Output coupling capacitor. Low frequency pole given by: fL e 1 RqRLC2 Typical Applications (Continued) TL/H/7934 – 8 FIGURE 4. LM2878 Servo Amplifier in Bridge Configuration TL/H/7934–7 FIGURE 3. Stereo Amplifier with AV e 200 6 Typical Applications (Continued) Truth Table VIN k (/4V a (/4V a to */4V a l */4V a TL/H/7934 – 9 FIGURE 5. Window Comparator Driving High, Low Lamps 7 High Low Off Off On On Off Off LM2878 Dual 5 Watt Power Audio Amplifier Physical Dimensions inches (millimeters) Single-In-Line Package (P) Order Number LM2878P NS Package Number P11A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 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