参数资料
型号: TLV1018-25YDCR
厂商: TEXAS INSTRUMENTS INC
元件分类: 音频/视频放大
英文描述: 1 CHANNEL, AUDIO AMPLIFIER, PBGA4
封装: GREEN, DSBGA-4
文件页数: 11/12页
文件大小: 615K
代理商: TLV1018-25YDCR
Low-Frequency Cut-Off Filter
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
Frequency (Hz)
G
a
in
d
B
-180
-135
-90
-45
0
45
90
135
180
P
h
a
s
e
°
Gain
Phase
10
100
1k
10k
100k
1M
Advantage of Three Pins
SLVS664A – OCTOBER 2008 – REVISED NOVEMBER 2008 .......................................................................................................................................... www.ti.com
Because the TLV1018-15 has a gain of 5.6 (15 dB) over the JFET, the output voltage of the microphone is
6.35 mVPP. By replacing the JFET with the TLV1018-15, the sensitivity of the microphone is –29 dBV/Pa
(–44 + 15).
To reduce noise on the output of the microphone, a low-cut filter is implemented in the TLV1018. This filter
reduces the effect of wind and handling noise.
It is also helpful to reduce the proximity effect in directional microphones. This effect occurs when the sound
source is very close to the microphone. The lower frequencies are amplified, which gives a bass sound. This
amplification can cause an overload, which results in a distortion of the signal.
Figure 5. Gain vs. Frequency
The TLV1018 is optimized to be used in audio-band applications. The TLV1018 provides a flat gain response
within the audio band and offers linearity and excellent temperature stability.
The TLV1018 ECM solution has three pins, instead of the two pins provided in the case of a JFET solution. The
third pin provides the advantage of a low supply current, high PSRR, and eliminates the need for additional
components.
Noise pick-up by a microphone in a cell phone is a well known problem. A conventional JFET circuit is sensitive
for noise pick-up because of its high output impedance. The output impedance is usually around 2.2 k
. By
providing separate output and supply pins a much lower output impedance is achieved and therefore is less
sensitive to noise pick-up.
RF noise is one of the noises caused by non-linear behavior. The non-linear behavior of the amplifier at high
frequencies, well above the usable bandwidth of the device, causes AM demodulation of high-frequency signals.
The AM modulation contained in such signals folds back into the audio band, thereby disturbing the intended
microphone signal. The GSM signal of a cell phone is such an AM-modulated signal. The modulation frequency
of 216 Hz and its harmonics can be observed in the audio band. This type of noise is called bumblebee noise.
8
Copyright 2008, Texas Instruments Incorporated
Product Folder Link(s): TLV1018
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