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AN-69

LM380

Power

Audio

Amplifier

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

2. A critical component is any component of a life

systems which, (a) are intended for surgical implant

support device or system whose failure to perform can

into the body, or (b) support or sustain life, and whose

be reasonably expected to cause the failure of the life

failure to perform, when properly used in accordance

support device or system, or to affect its safety or

with instructions for use provided in the labeling, can

effectiveness.

be reasonably expected to result in a significant injury
to the user.

National Semiconductor

National Semiconductor

National Semiconductor

National Semiconductor

Corporation

Europe

Hong Kong Ltd.

Japan Ltd.

1111 West Bardin Road

Fax: (

a

49) 0-180-530 85 86

13th Floor, Straight Block,

Tel: 81-043-299-2309

Arlington, TX 76017

Email: cnjwge

@

tevm2.nsc.com

Ocean Centre, 5 Canton Rd.

Fax: 81-043-299-2408

Tel: 1(800) 272-9959

Deutsch Tel: (

a

49) 0-180-530 85 85

Tsimshatsui, Kowloon

Fax: 1(800) 737-7018

English

Tel: (

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49) 0-180-532 78 32

Hong Kong

Fran

3

ais Tel: (

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49) 0-180-532 93 58

Tel: (852) 2737-1600

Italiano

Tel: (

a

49) 0-180-534 16 80

Fax: (852) 2736-9960

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.

Summary of Contents for LM380

Page 1: ... half supply since R1 e 2 R2 Figure 1 The second stage is a common emitter voltage gain amplifi er with a current source load Internal compensation is pro vided by the pole splitting capacitor CÊ Pole splitting com pensation is used to preserve wide power bandwidth 100 kHz at 2W 8X The output is a quasi complementary pair emitter follower The amplifier gain is internally fixed to 34 dB or 50 This ...

Page 2: ...kage will support 3 watts dissipation at 50 C am bient or 3 7 watts at 25 C ambient Figure 2 shows the maximum package dissipation versus ambient temperature for various amounts of heat sinking TL H 7380 2 FIGURE 2 Device Dissipation vs Ambient Temperature Figures 3a b and c show device dissipation versus output power for various supply voltages and loads TL H 7380 3 FIGURE 3a Device Dissipation v...

Page 3: ...ting input is used the inverting input is left floating When the inverting input is used and the non in verting input is left floating the amplifier may be found to be sensitive to board layout since stray coupling to the floating input is positive feedback This can be avoided by employ ing one of three alternatives 1 AC grounding the unused input with a small capacitor This is preferred when usin...

Page 4: ...ume and Tone Control This common mode volume control can be combined with a common mode tone control as seen in Figure 10 This circuit has a distinct advantage over the circuit of Fig ure 7 when transducers of high source impedance are used in that the full input impedance of the amplifier is realized It also has an advantage with transducers of low source im pedance since the signal attenuation o...

Page 5: ...ereby increasing the power capability by a factor of four over the single amplifier However in most cases the package dissipation will be the first parameter limiting power delivered to the load When this is the case the power capability of the bridge will be only twice that of TL H 7380 17 FIGURE 15A 8X Load the single amplifier Figures 15A and B show output power versus device package dissipatio...

Page 6: ...r T1 A turns ratio of 25 and a device gain of 50 allows a maxi mum loop gain of 1250 RV provides a common mode volume control Switching S1 to the listen position reverses the role of the master and remote speakers LOW COST DUAL SUPPLY The circuit shown in Figure 19 demonstrates a minimum parts count method of symmetrically splitting a supply volt age Unlike the normal R C and power zener diode tec...

Page 7: ... value of R2 is determined by the product of the gate reverse leakage IGSS and R2 This voltage should be 10 to 100 times smaller than VP The output impedance of the FET source follower is Ro e 1 gm 11 so that the determining resistance for the interstage RC time constant is the input resistance of the LM380 BOOSTED GAIN USING POSITIVE FEEDBACK For applications requiring gains higher than the inter...

Page 8: ...ions for use provided in the labeling can effectiveness be reasonably expected to result in a significant injury to the user National Semiconductor National Semiconductor National Semiconductor National Semiconductor Corporation Europe Hong Kong Ltd Japan Ltd 1111 West Bardin Road Fax a49 0 180 530 85 86 13th Floor Straight Block Tel 81 043 299 2309 Arlington TX 76017 Email cnjwge tevm2 nsc com Oc...

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