Electronic Components Datasheet Search |
|
LM1896 Datasheet(PDF) 7 Page - Texas Instruments |
|
LM1896 Datasheet(HTML) 7 Page - Texas Instruments |
7 / 12 page Application Hints AM Radios The LM1896LM2896 has been designed fo fill a wide range of audio power applications A common problem with IC audio power amplifiers has been poor signal-to-noise per- formance when used in AM radio applications In a typical radio application the loopstick antenna is in close proximity to the audio amplifer Current flowing in the speaker and power supply leads can cause electromagnetic coupling to the loopstick resulting in system oscillation In addition most audio power amplifiers are not optimized for lowest noise because of compensation requirements If noise from the audio amplifier radiates into the AM section the sensitiv- ity and signal-to-noise ratio will be degraded The LM1896 exhibits extremely low wideband noise due in part to an external capacitor C5 which is used to tailor the bandwidth The circuit shown in Figure 2 is capable of a signal-to-noise ratio in excess of 60 dB referred to 50 mW Capacitor C5 not only limits the closed loop bandwidth it also provides overall loop compensation Neglecting C2 in Figure 2 the gain is AV(S) e S a AV 0o S a 0o where AV e R2 a R5 R2 0o e 1 R5C5 A curve of b3dBBW(0o)vsAV is shown in the Typical Performance Curves Figure 3 shows a plot of recovered audio as a function of field strength in mVM The receiver section in this example is an LM3820 The power amplifier is located about two inches from the loopstick antenna Speaker leads run paral- lel to the loopstick and are 18 inch from it Referenced to a 20 dB SN ratio the improvement in noise performance over conventional designs is about 10 dB This corresponds to an increase in usable sensitivity of about 85 dB Bridge Amplifiers The LM1896LM2896 can be used in the bridge mode as a monaural power amplifier In addition to much higher power output the bridge configuration does not require output cou- pling capacitors The load is connected directly between the amplifier outputs as shown in Figure 4 Amp 1 has a voltage gain set by 1 a R5R2 The output of amp 1 drives amp 2 which is configured as an inverting amplifier with unity gain Because of this phase inversion in amp 2 there isa6dB increase in voltage gain referenced to Vi The voltage gain in bridge is Vo Vi e 2 1aR5R2 J CB is used to prevent DC voltage on the output of amp 1 from causing offset in amp 2 Low frequency response is influenced by fL e 1 2q RBCB Several precautions should be observed when using the LM1896LM2896 in bridge configuration Because the am- plifiers are driving the load out of phase an 8X speaker will appear as a 4X load and a 4X speaker will appear as a 2X load Power dissipation is twice as severe in this situation For example if VS e 6V and RL e 8X bridged then the maximum dissipation is PD e V 2 S 20 RL c 2 e 62 20 c 4 c 2 PD e 09 Watts This amount of dissipation is equivalent to driving two 4X loads in the stereo configuration When adjusting the frequency response in the bridge config- uration R5C5 and R10C10 form a 2 pole cascade and the b 3 dB bandwidth is actually shifted to a lower frequency BW e 0707 2qRC where R e feedback resistor C e feedback capacitor To measure the output voltage a floating or differential me- ter should be used because a prolonged output short will over dissipate the package Figure 1 shows the complete bridge amplifier TLH7920 – 9 FIGURE 3 Improved AM Sensitivity over Conventional Design 6 |
Similar Part No. - LM1896 |
|
Similar Description - LM1896 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |