Power Bandwidth - PiezoDrive TD250 Manual

7

Power Bandwidth

With a capacitive load, the peak load current for a sine-wave is
where �� is the peak-to-peak output voltage, �� is the load capacitance, and �� is the frequency.
�� ��
Given a peak current limit ��
TD250 is protected by both peak and average current limits. The average current ��
the average positive or negative current. For example, for a sine-wave
Therefore, for a sine-wave ��
maximum frequency sine-wave, or power bandwidth of the TD250, is equal to
The above result is true for any periodic waveform such as triangular signals. The RMS current for a
sine-wave can also be related to the average current,
The power bandwidths for a range of load capacitance values are listed below.
��
����
, the maximum frequency is therefore �� = ��
����
��
1
sin ( �� ) ����
�� = ∫ ��
����+ ����
2��
0
= �� /��. Since the average current limit of the TD250 is 10 mA, the
����+ ����
��
Load
Cap. 200
No Load 50 kHz
12 kHz
3 nF
4.5 kHz
10 nF
1.6 kHz
30 nF
490 Hz
100 nF
160 Hz
300 nF
50 Hz
1 uF
Table 1. Power bandwidth versus load capacitance
= ±�� ������
����
��
����
[ −������ ]
=
2��
0.01
�� = .
�� ��
�� ��
√ 2
= �� .
���� ������
��
Peak to Peak Voltage
300 400
33 kHz 25 kHz
8.3 kHz 6.2 kHz
3.0 kHz 2.2 kHz
1.0 kHz 800 Hz
330 Hz 240 Hz
110 Hz 83 Hz
33 Hz 25 Hz
8
/�� ����. However, the
���� �� ��
is defined as
����+
��
����
��
= .
0
��
500
20 kHz
5.0 kHz
1.8 kHz
640 Hz
190 Hz
66 Hz
20 Hz