International Journal of Circuit Theory and Applications ( IF 2.3 ) Pub Date : 2020-09-09 , DOI: 10.1002/cta.2869 Hanumantha Rao G 1
The main intention of our work in [1] was to design a low voltage, low power low‐pass filter for ECG signal front‐end processing. For this purpose, we proposed a bulk‐driven voltage follower (Figure 1(a) in [1]). We considered Ref [18] (cited in our paper and given below as [3]) by Sawigun et al., as the base paper. The circuit in [18] is a gate driven with a 0.5 V supply but we designed a bulk driven circuit as the power supply used is only 0.3 V.
Surprisingly, it looks similar to the circuit in [2] (Figure 1(a)), due to its simple structure with only four transistors in both circuits. In fact, most of the low voltage bulk‐driven circuits, especially differential amplifiers, use four transistors in their input stages and look similar. In addition, a voltage follower is obtained from a differential amplifier by shorting its output to negative input. Hence, both circuits look similar.
- In our proposed circuit, same biasing current (Io) is mirrored to both legs of differential amplifier whereas the circuit in [2] uses two different biasing currents (through VB1 and VB2) for two legs.
- [2] uses a compensating capacitor for high frequency operation. Hence the analysis of the two circuits will be different.
- We have connected a capacitor at the output to make our proposed circuit a first order lowpass filter. Further, a fourth order low‐pass filter is designed from this first order filter. The circuit in [2] is designed entirely for a different application. It does not have a capacitor at the output stage and it is used in the design of a class‐AB amplifier and further used in the design of an op‐amp.
- Our circuit operates with a supply voltage of 0.3 V and the circuit in [2] operates with a supply voltage of 0.5 V.
- The sizes of transistors are different in both circuits; hence, their responses will be obviously different. Small signal and noise modelling are also different in the two papers.
中文翻译：
作者的回应
[ 1 ]中我们的工作的主要目的是设计一种用于ECG信号前端处理的低电压，低功耗低通滤波器。为此，我们提出了一种批量驱动的电压跟随器（[ 1 ]中的图1（a））。我们将Sawigun等人的参考文献[18]（在我们的论文中引用并在下面以[ 3 ]给出）作为基础论文。[18]中的电路是用0.5 V电源驱动的栅极，但是我们设计了大容量驱动电路，因为所使用的电源仅为0.3V。
令人惊讶的是，由于其结构简单，两个电路中只有四个晶体管，因此它看起来与[ 2 ]中的电路类似（图1（a））。实际上，大多数低压大容量驱动电路，特别是差分放大器，在其输入级使用四个晶体管，外观相似。此外，通过将差分放大器的输出短路至负输入，可以从差分放大器获得电压跟随器。因此，两个电路看起来相似。
- 在我们提出的电路中，相同的偏置电流（Io）反映到差分放大器的两个支路，而[ 2 ]中的电路为两个支路使用两个不同的偏置电流（通过VB1和VB2）。
- [ 2 ]使用补偿电容器进行高频操作。因此，两个电路的分析将不同。
- 我们在输出端连接了一个电容器，使我们提出的电路成为一阶低通滤波器。此外，根据该一阶滤波器设计了一个四阶低通滤波器。[ 2 ]中的电路完全是为不同的应用设计的。它在输出级没有电容器，用于AB类放大器的设计中，并进一步用于运算放大器的设计中。
- 我们的电路在0.3 V的电源电压下工作，[ 2 ]中的电路在0.5 V的电源电压下工作。
- 两种电路中晶体管的大小都不同。因此，他们的反应将明显不同。这两篇论文中的小信号和噪声建模也有所不同。
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