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TEA1068 数据表(PDF) 7 Page - NXP Semiconductors |
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TEA1068 数据表(HTML) 7 Page - NXP Semiconductors |
7 / 24 page 1996 Apr 23 7 Philips Semiconductors Product specification Versatile telephone transmission circuit with dialler interface TEA1068 If fixed values are chosen for R1, R2, R3 and R9, then condition (1) will always be fulfilled, provided that R8//Zbal << R3. To obtain optimum side-tone suppression, condition (2) has to be fulfilled, resulting in: Zbal = (R8/R1) Zline = k × Zline, where k is a scale factor: k = (R8/R1). Scale factor k (dependent on the value of R8) must be chosen to meet the following criteria: 1. Compatibility with a standard capacitor from the E6 or E12 range for Zbal 2. Zbal//R8<< R3 to fulfil condition (1) and thus ensuring correct anti-side-tone bridge operation 3. Zbal +R8>> R9 to avoid influencing the transmitter gain. In practice, Zline varies greatly with the line length and cable type; consequently, an average value has to be chosen for Zbal, thus giving an optimum setting for short or long lines. Example: the balanced line impedance (Zbal) at which the optimum suppression is preset can be calculated by: Assume Zline = 210 Ω + (1265 Ω/140 nF), representing a 5 km line of 0.5 mm diameter, copper, twisted-pair cable matched to 600 Ω (176 Ω/km; 38 nF/km). When k = 0.64, then R8 = 390 Ω; Zbal = 130 Ω + (820 Ω//220 nF). The anti-side-tone network for the TEA1060 family shown in Fig.5 attenuates the signal received from the line by 32 dB before it enters the receiving amplifier. The attenuation is almost constant over the whole audio frequency range. Figure 6 shows a conventional Wheatstone bridge anti-side-tone circuit that can be used as an alternative. Both bridge types can be used with either resistive or complex set impedances. Fig.5 Equivalent circuit of TEA1060 family anti-side-tone bridge. handbook, full pagewidth MSA500 R1 R2 R9 R3 IR R8 VEE SLPE LN Zline Rt im Zbal |
类似零件编号 - TEA1068 |
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类似说明 - TEA1068 |
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