Datasheet SA571 (ON Semiconductor) - 6
| Fabricante | ON Semiconductor |
| Descripción | Compandor |
| Páginas / Página | 12 / 6 — SA571. Figure 7. Basic Compressor. Circuit Details − Rectifier. Figure 6. … |
| Formato / tamaño de archivo | PDF / 230 Kb |
| Idioma del documento | Inglés |
SA571. Figure 7. Basic Compressor. Circuit Details − Rectifier. Figure 6. Basic Expander. Figure 8. Rectifier Concept
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SA571
Figure 6 shows how the circuit is hooked up to realize an R2 DG expandor. The input signal, VIN, is applied to the inputs of both the rectifier and the DG cell. When the input signal R drops by 6.0 dB, the gain control current will drop by a factor 1 of 2, and so the gain will drop 6.0 dB. The output level at CRECT * C * F V R * * OUT will thus drop 12 dB, giving us the desired 2−to−1 DC RDC expansion. C * C * IN R DC 3 V R − OUT 3 VIN + VREF R4 *CIN1 R2 DG
−
R I 2 B Ǔ12
+
V V OUT NOTE: GAIN + ǒ R1 IN 2R V R 3 INavg 4 I *C V B = 140mA IN2 R REF 1 *EXTERNAL COMPONENTS
Figure 7. Basic Compressor
*CRECT
Circuit Details − Rectifier
Figure 8 shows the concept behind the full−wave V (avg)Ǔ2 NOTE: GAIN + ǒ2 R3 IN R R I averaging rectifier. The input current to the summing node 1 2 B IB = 140mA of the op amp, VIN/R1, is supplied by the output of the op *EXTERNAL COMPONENTS amp. If we can mirror the op amp output current into a unipolar current, we will have an ideal rectifier. The output
Figure 6. Basic Expander
current is averaged by R5, CR, which set the averaging time constant, and then mirrored with a gain of 2 to become I Figure 7 shows the hook−up for a compressor. This is G, the gain control current. essentially an expandor placed in the feedback loop of the op amp. The DG cell is setup to provide AC feedback only, so I = V V+ IN / R1 a separate DC feedback loop is provided by the two RDC and CDC. The values of RDC will determine the DC bias at the output of the op amp. The output will bias to: R1 − R ) R Ǔ VIN + V DC + ǒ1 ) DC1 DC2 V OUT R R REF 5 4 10kW CR IG R Ǔ V DC + ǒ1 ) DCTOT 1.8V OUT 30kW The output of the expander will bias up to: R Ǔ V DC + ǒ 1 ) 3 V OUT R REF 4
Figure 8. Rectifier Concept
V DC + ǒ1 ) 20kWǓ 1.8V + 3.0V OUT 30kW The output will bias to 3.0 V when the internal resistors are used. External resistors may be placed in series with R3, (which will affect the gain), or in parallel with R4 to raise the DC bias to any desired value.
http://onsemi.com 6
SA571
Figure 6 shows how the circuit is hooked up to realize an R2 DG expandor. The input signal, VIN, is applied to the inputs of both the rectifier and the DG cell. When the input signal R drops by 6.0 dB, the gain control current will drop by a factor 1 of 2, and so the gain will drop 6.0 dB. The output level at CRECT * C * F V R * * OUT will thus drop 12 dB, giving us the desired 2−to−1 DC RDC expansion. C * C * IN R DC 3 V R − OUT 3 VIN + VREF R4 *CIN1 R2 DG
−
R I 2 B Ǔ12
+
V V OUT NOTE: GAIN + ǒ R1 IN 2R V R 3 INavg 4 I *C V B = 140mA IN2 R REF 1 *EXTERNAL COMPONENTS
Figure 7. Basic Compressor
*CRECT
Circuit Details − Rectifier
Figure 8 shows the concept behind the full−wave V (avg)Ǔ2 NOTE: GAIN + ǒ2 R3 IN R R I averaging rectifier. The input current to the summing node 1 2 B IB = 140mA of the op amp, VIN/R1, is supplied by the output of the op *EXTERNAL COMPONENTS amp. If we can mirror the op amp output current into a unipolar current, we will have an ideal rectifier. The output
Figure 6. Basic Expander
current is averaged by R5, CR, which set the averaging time constant, and then mirrored with a gain of 2 to become I Figure 7 shows the hook−up for a compressor. This is G, the gain control current. essentially an expandor placed in the feedback loop of the op amp. The DG cell is setup to provide AC feedback only, so I = V V+ IN / R1 a separate DC feedback loop is provided by the two RDC and CDC. The values of RDC will determine the DC bias at the output of the op amp. The output will bias to: R1 − R ) R Ǔ VIN + V DC + ǒ1 ) DC1 DC2 V OUT R R REF 5 4 10kW CR IG R Ǔ V DC + ǒ1 ) DCTOT 1.8V OUT 30kW The output of the expander will bias up to: R Ǔ V DC + ǒ 1 ) 3 V OUT R REF 4
Figure 8. Rectifier Concept
V DC + ǒ1 ) 20kWǓ 1.8V + 3.0V OUT 30kW The output will bias to 3.0 V when the internal resistors are used. External resistors may be placed in series with R3, (which will affect the gain), or in parallel with R4 to raise the DC bias to any desired value.
http://onsemi.com 6