Os motores de busca de Datasheet de Componentes eletrônicos |
|
LM1894N Folha de dados(PDF) 7 Page - National Semiconductor (TI) |
|
|
LM1894N Folha de dados(HTML) 7 Page - National Semiconductor (TI) |
7 / 10 page Application Hints The DNR system should always be placed before tone and volume controls as shown in Figure 1. This is because any adjustment of these controls would alter the noise floor seen by the DNR control path. The sensitivity resistors R1 and R2 may need to be switched with the input selector, depending on the noise floors of different sources, i.e., tape, FM, phono. To determine the value of R1 and R2 in a tape system for in- stance; apply tape noise (no program material) and adjust the ratio of R1 and R2 to open slightly the bandwidth of the main signal path. This can easily be done by viewing the ca- pacitor voltage of pin 10 with an oscilloscope, or by using the circuit of Figure 5. This circuit gives an LED display of the voltage on the peak detector capacitor. Adjust the values of R1 and R2 (their sum is always 1 k Ω) to light the LEDs of pin 1 and pin 18. The LED bar graph does not indicate signal level, but rather instantaneous bandwidth of the two filters; it should not be used as a signal-level indicator. For greater flexibility in setting the bandwidth sensitivity, R1 and R2 could be replaced bya1k Ω potentiometer. To change the minimum and maximum value of bandwidth, the integrating capacitors, C3 and C12, can be scaled up or down. Since the bandwidth is inversely proportional to the capacitance, changing this 0.0039 µF capacitor to 0.0033 µF will change the typical bandwidth from 965 Hz–34 kHz to 1.1 kHz–40 kHz. With C3 and C12 set at 0.0033 µF, the maxi- mum bandwidth is typically 34 kHz. A double pole double throw switch can be used to completely bypass DNR. The capacitor on pin 10 in conjunction with internal resistors sets the attack and decay times. The attack time can be al- tered by changing the size of C10. Decay times can be de- creased by paralleling a resistor with C10, and increased by increasing the value of C10. When measuring the amount of noise reduction of the DNR system, the frequency response of the cassette should be flat to 10 kHz. The CCIR weighting network has substantial gain to 8 kHz and any additional roll-off in the cassette player will reduce the benefits of DNR noise reduction. A typical signal-to-noise measurement circuit is shown in Figure 6. The DNR system should be switched from maximum band- width to nominal bandwidth with tape noise as a signal source. The reduction in measured noise is the signal-to-noise ratio improvement. DS007918-10 FIGURE 5. Bar Graph Display of Peak Detector Voltage DS007918-11 FIGURE 6. Technique for Measuring S/N Improvement of the DNR System www.national.com 7 |
Nº de peça semelhante - LM1894N |
|
Descrição semelhante - LM1894N |
|
|
Ligação URL |
Privacy Policy |
ALLDATASHEETPT.COM |
ALLDATASHEET é útil para você? [ DONATE ] |
Sobre Alldatasheet | Publicidade | Contato conosco | Privacy Policy | roca de Link | Lista de Fabricantes 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 |