BD7830NUV Rohm, BD7830NUV Datasheet - Page 9

• Manufacturer Part Number: BD7830NUV
• Description: 1.1W to1.5W Monaural Speaker Amplifier
• Manufacturer: Rohm

●Ci
●Ri
●Rf
●Cf
BD7830NUV
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www.rohm.com
This is a DC cut-off input coupling capacitor for the amp input pin.
This includes an Ri and a high-pass filter. The cut-off frequency is calculated as follows.
Capacitors of a certain size are required for coupling without attenuation of low frequencies, but in most cases of speakers
used in portable equipment, it is nearly impossible to reproduce signals in the 100 to 200 Hz range or below. Even when a
larger capacitor is used instead, it may not improve system performance. Also, pop sounds can affect the capacitance (Ci) of
the capacitor. A larger coupling capacitor requires a greater charge to reach the bias DC voltage (normally 1/2 VCC).
Because this charge current is supplied from the output due to routing of feedback, pop sounds occur easily at startup.
Consequently, pop sounds can be minimized by selecting the smallest capacitor that still has the required low-frequency
response.
This is inverting input resistance, which sets the closed loop gain in conjunction with Rf.
This is feedback resistance, which sets closed loop gain in conjunction with Rf. The amp gain is set using the following
formula.
This is a feedback capacitor, which is used to cut high frequencies.
This includes Rf and a low-pass filter. The cut-off frequency is calculated as follows.
Gain = 20log
f
f
CL
CL
=
=
Rf
Ri
2π×Ri×Ci
2π×Ri×Ci
1
1
[dB]
-10
-2
-4
-6
-8
4
2
0
10
Ci – Low Frequency Characteristics
[Hz]
[Hz]
100
Ci:0.22uF
Ci-Frequency characteristic
Ci:0.1uF
Ci:0.047uF
Frequency[Hz]
9/17
1k
10k
100k
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Technical Note
2010.06 - Rev.A