digital-brain/content/zettels/transconductance_amplifiers.md

+++ title = "Transconductance Amplifiers" author = ["Dehaeze Thomas"] draft = false category = "equipment" +++

Tags

[Electronics]({{< relref "electronics.md" >}}), [Voice Coil Actuators]({{< relref "voice_coil_actuators.md" >}})

Description

A Transconductance Amplifier converts the control voltage into current with a current source characteristic.

Such a converter is called a voltage-to-current converter, also named a voltage-controlled current source or transconductance amplifier.

Such amplifier is used to control motors (e.g. voice coil, BLDC, stepper motors, ...).

Specifications

Noise

BL = 20; % [N/A]
m = 1; % [kg]

freq = logspace(0,4,1000); % [Hz]

%% Current noise of the amplifier
I_asd = 1e-6*ones(size(freq)); % [A/sqrt(Hz)]

x_asd = I_asd*(BL/m)./(2*pi*freq).^2;

figure;
plot(freq, x_asd)
xlabel("Frequency [Hz]");
ylabel("ASD [$m/\sqrt{Hz}$]");
set(gca, 'Xscale', 'log');
set(gca, 'Yscale', 'log');

figure;
plot(freq, sqrt(flip(-cumtrapz(flip(freq), flip(x_asd.^2)))))
xlabel("Frequency [Hz]");
ylabel("Cumulative Amplitude Spectrum [m rms]");
set(gca, 'Xscale', 'log');
set(gca, 'Yscale', 'log');

Manufacturers

Table 1: Drivers with integrated controllers

Model	Manufacturer	Linear / PWM	Axes	Interfaces	Feedback	Current Bandwidth	ASD at 1kHz [A/sqrt(Hz)]
Apogee	Prodrive	PWM	1 to 3	+/-10V 16bits	Encoder	7kHz	1e-6
S3-400/8	Prodrive	PWM	1	+/-10V	Encoder	1kHz	1e-4
LWM7S	Macon	Linear	1		Encoder/Hall
Soloist ML	Aerotech	Linear	1	+/-10V 16bits	Encoder/Hall
Automation1 XL4s	Aerotech	Linear	1 (voice coil)	+/-10V 16bits	?
Automation1 XL2e	Aerotech	Linear	1	+/-10V 16bits	Encoder/Hall	2.5kHz
EM-356B	Electromen	PWM	1	0-10V	Hall
azbh10a4	AMC	PWM	1	+/-10V	Hall
X-MCC	Zaber	??	1 to 4
TA310	TrustAutomation	Linear	1	+/-10V	Hall	5kHz

Table 2: Pure Drivers

Model	Manufacturer	Linear / PWM	Axes	Interfaces	Current Bandwidth	Max Current	ASD at 1kHz [A/sqrt(Hz)]
LA300	Varedan	Linear	3	+/-10V	10kHz	4A
LA24	Cedrat	Linear	3	+/-10V	35kHz	1.5A
CMAu10	Cedrat	Linear	1	+/-10V	5kHz	0.5A
TA115 and TA105	TrustAutomation	Linear	1	+/-10V	5kHz		1e-6
SMA6520	Glentek	Linear	1 Brushless (3 phases)	+/-10V	10kHz
SMA5005	Glentek	Linear	1	+/-10V	10kHz

Bibliography