Keysight Labs | Attenuators and Preamps - Oscilloscope Front End Design (part 3) @KeysightLabs | Uploaded July 2017 | Updated October 2024, 7 hours ago.
What's behind your oscilloscope's BNC? Analog IC designer Mike Lujan lays it out - part 2 of "Oscilloscope Front End Design" talk
Click to subscribe! ► bit.ly/Scopes_Sub ◄
Part 1: What is an Oscilloscope?
youtu.be/o-JvRlKCOaM
Part 2: Hardware Layout - What's Behind the BNC?
youtu.be/EaBSN6dpqP8
Part 3: Attenuators and Preamps
youtu.be/gPQRSWcRaFg
Part 4: Signal Offsets and Filters
youtu.be/1sVEWzMjkBo
Part 5: Probing
youtu.be/pdbzIwelCL4
What technologies are used for oscilloscope attenuators and oscilloscope preamps?
---------------------
Attenuators
--------------------
There are two main things that influence attenuator technologies. The main limiter is device parasitic capacitance and inductance, either in the attenuator itself or in it's support circuitry.
The most basic attenuator is a relay with a resistive divider network. The bandwidth is limited because there is a long signal path required.
A solid state attenuator is often good up to several GHz. They use GaAs MESFET with stepped attenuation. They are similar to a MOSFET, and if the device is on it provides near zero impedance, and when on it switches to high impedance. The bandwidth can be limited by capacitance. At higher frequencies, the higher frequency components can "blow through" the capacitors and the attenuator becomes less effective.
The other limitation is that it has a voltage limit. With too high of a voltage, the system can be non-linear or even damaged.
For the highest bandwidth oscilloscopes, a coaxial stepped attenuator is used. It uses an RF input and gives the appearance of 50 ohms up to very high frequencies.
---------------------
Preamps
---------------------
SiGe BiCMOS bandwidths go up to 30 GHz depending on technology node and packaging. A standard QFN can go up to 8 GHz, but with custom IC packaging you can get much higher using custom launches and bypass circuitry. The impedances are also much easier to control.
For very high performance, InP HBT preamps can be used beyond 50 GHz. Indium Phosphide processes allow you to design very fast transistors that are faster than germanium doped silicon.
---------------------
Links
---------------------
Twitter: @DanielBogdanoff twitter.com/DanielBogdanoff
Learn more about using oscilloscopes:
oscilloscopelearningcenter.com
Check out the EEs Talk Tech electrical engineering podcast:
youtube.com/playlist?list=PLzHyxysSubUnAMeCIi2-S0Vm7YtSAGqx_
The 2-Minute Guru Season 2 playlist:
youtube.com/playlist?list=PLzHyxysSubUlqBguuVZCeNn47GSK8rcso
The 2-Minute Guru Season 1 playlist:
youtube.com/playlist?list=PLzHyxysSubUkc5nurngzgkd2ZxJsHdJAb
More about Keysight oscilloscopes:
bit.ly/SCOPES
Check out our blog:
bit.ly/ScopesBlog
Like our Facebook page:
facebook.com/keysightbench
#tutorial #electronics #oscilloscopes #oscilloscope #engineering
#design #IC #ASIC #electrical #test #preamp #attenuators
What's behind your oscilloscope's BNC? Analog IC designer Mike Lujan lays it out - part 2 of "Oscilloscope Front End Design" talk
Click to subscribe! ► bit.ly/Scopes_Sub ◄
Part 1: What is an Oscilloscope?
youtu.be/o-JvRlKCOaM
Part 2: Hardware Layout - What's Behind the BNC?
youtu.be/EaBSN6dpqP8
Part 3: Attenuators and Preamps
youtu.be/gPQRSWcRaFg
Part 4: Signal Offsets and Filters
youtu.be/1sVEWzMjkBo
Part 5: Probing
youtu.be/pdbzIwelCL4
What technologies are used for oscilloscope attenuators and oscilloscope preamps?
---------------------
Attenuators
--------------------
There are two main things that influence attenuator technologies. The main limiter is device parasitic capacitance and inductance, either in the attenuator itself or in it's support circuitry.
The most basic attenuator is a relay with a resistive divider network. The bandwidth is limited because there is a long signal path required.
A solid state attenuator is often good up to several GHz. They use GaAs MESFET with stepped attenuation. They are similar to a MOSFET, and if the device is on it provides near zero impedance, and when on it switches to high impedance. The bandwidth can be limited by capacitance. At higher frequencies, the higher frequency components can "blow through" the capacitors and the attenuator becomes less effective.
The other limitation is that it has a voltage limit. With too high of a voltage, the system can be non-linear or even damaged.
For the highest bandwidth oscilloscopes, a coaxial stepped attenuator is used. It uses an RF input and gives the appearance of 50 ohms up to very high frequencies.
---------------------
Preamps
---------------------
SiGe BiCMOS bandwidths go up to 30 GHz depending on technology node and packaging. A standard QFN can go up to 8 GHz, but with custom IC packaging you can get much higher using custom launches and bypass circuitry. The impedances are also much easier to control.
For very high performance, InP HBT preamps can be used beyond 50 GHz. Indium Phosphide processes allow you to design very fast transistors that are faster than germanium doped silicon.
---------------------
Links
---------------------
Twitter: @DanielBogdanoff twitter.com/DanielBogdanoff
Learn more about using oscilloscopes:
oscilloscopelearningcenter.com
Check out the EEs Talk Tech electrical engineering podcast:
youtube.com/playlist?list=PLzHyxysSubUnAMeCIi2-S0Vm7YtSAGqx_
The 2-Minute Guru Season 2 playlist:
youtube.com/playlist?list=PLzHyxysSubUlqBguuVZCeNn47GSK8rcso
The 2-Minute Guru Season 1 playlist:
youtube.com/playlist?list=PLzHyxysSubUkc5nurngzgkd2ZxJsHdJAb
More about Keysight oscilloscopes:
bit.ly/SCOPES
Check out our blog:
bit.ly/ScopesBlog
Like our Facebook page:
facebook.com/keysightbench
#tutorial #electronics #oscilloscopes #oscilloscope #engineering
#design #IC #ASIC #electrical #test #preamp #attenuators
