real life method to properly biasing an amplyfier - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: September 04, 2024, 06:18:14 pm
content: Hello ,I have the following amplifyer PMA5-83-2W+ link shown below.I am building a sequencer for this device.The problem is that i dont have any data regarding what will be the Load .I dont have any model, The data sheet doesnt say what is the equivalent gate and drain loads.The manufacturer doesnt have any answers.So I suppose I am not the first person who doesnt have any simulation model of the amplyier and manages to design a sequencer for it.Is there some methods I could use?Thanks.https://www.minicircuits.com/pdfs/PMA5-83-2W+.pdf

author: David Hess
author_rank: Super Contributor
timestamp: September 05, 2024, 12:39:07 am
content: I do not see what the problem is. You do not need to know the source or load impedances to design and implement the power supply sequencing.

author: coppercone2
author_rank: Super Contributor
timestamp: September 05, 2024, 01:54:27 am
content: it looks like the thing is having trouble getting out of Antarctica

author: CaptDon
author_rank: Super Contributor
timestamp: September 05, 2024, 02:09:19 am
content: Where does VDD hook up? I don't see it. Looks like a pain in the butt to use if I have to be that careful with the power rails. Does it have some special function that can't be replaced with a more robust 'nearly indestructable' part that doesn't care about power sequencing??

author: Someone
author_rank: Super Contributor
timestamp: September 05, 2024, 03:35:40 am
content: Quote from: john23 on September 04, 2024, 06:18:14 pmWhere is the drain load?The data sheet has more than enough detail to design a suitable sequencer + power drivers/regulators.For those unfamiliar with the OP. There is some unstated mystery project involving (reverse engineering?) a pile of RF magic, but the OP doesnt seem familiar with basic electronics:https://www.eevblog.com/forum/projects/bjt-invertive-switching-logic-question/https://www.eevblog.com/forum/projects/digital-buffer-delay-components-reply-thread-starteryef-smith-start-date2-minu/https://www.eevblog.com/forum/projects/modeling-the-effect-of-pullup-resistor-to-current-drive-a-load/https://www.eevblog.com/forum/projects/pure-dc-voltage-delay-mechanism-question/https://www.eevblog.com/forum/projects/purpose-of-opamp-in-biasing-tga2227/and already has the general problem(s) outlined in this thread answered previously:https://www.eevblog.com/forum/projects/dc-dc-recomendations-for-pma5-83-2w-sequencer/https://www.eevblog.com/forum/projects/proper-charging-and-discharging-of-dc-dc-using-mosfet/

author: john23
author_rank: Frequent Contributor
timestamp: September 05, 2024, 09:06:09 am
content: Why I dont need , I have designed a sequencer and i have a pin going to Vg and a pin going into the drain.I need to know how when the signal will be passed to the load.

author: Someone
author_rank: Super Contributor
timestamp: September 05, 2024, 09:33:23 am
content: Quote from: john23 on September 05, 2024, 09:06:09 amPMA5-83-2W+ does not haveadrain.

author: john23
author_rank: Frequent Contributor
timestamp: September 05, 2024, 09:45:01 am
content: Yes i mend in generalIn here i have Vg1 Vg2 Vdd pins.I need to know what load they will exibit to my sequencer.Thanks.

author: Someone
author_rank: Super Contributor
timestamp: September 05, 2024, 10:07:36 am
content: Quote from: john23 on September 05, 2024, 09:45:01 amThat is explicitly described in the data sheet.

author: eutectique
author_rank: Frequent Contributor
timestamp: September 05, 2024, 10:17:39 am
content: Quote from: john23 on September 05, 2024, 09:45:01 amPage 3 of the datasheet, table "ELECTRICAL SPECIFICATIONS1 AT 25°C, VDD= +12 V, UNLESS NOTED OTHERWISE (CONTINUED)", lines "Device Operating Current (IDD)", "Gate Current (IG1)", and "Gate Current (IG2)".Anything else?

author: john23
author_rank: Frequent Contributor
timestamp: September 05, 2024, 04:54:15 pm
content: Hello , so Its pure resistive load for example regarding Vdd 12V/0.4=30Ohm .SHown below a partially working sequencer and the outputs are shown in red arrows.So for example My load at Vdd will be 30OhmBut in real life as you can see in the data sheet photo I have capacitances too.Capacitance on the load will slow down the pulse on one hand but will make the voltage stable.How do you reccomend to see how much capacitance i need to put at the end of the Vg1 Vdd ?The data sheet is talking about manual switching of the voltages here i have sequences and wrong capacitances at the load could ruing the sequence.Thanks.

author: Someone
author_rank: Super Contributor
timestamp: September 05, 2024, 09:44:46 pm
content: Quote from: john23 on September 05, 2024, 04:54:15 pmIf the sequence is wrong then it is your circuit (that you reveal afterwards) that is at fault.Quote from: john23 on September 05, 2024, 04:54:15 pmNoQuote from: john23 on September 05, 2024, 04:54:15 pmThat is dependent on yourspecificapplication (which you won't tell us about) so we cannot say. Only you can find this out from either experimentation, or using experience.

author: john23
author_rank: Frequent Contributor
timestamp: September 06, 2024, 12:25:28 pm
content: so Its pure resistive load for example regarding Vdd 12V/0.4=30Ohm-NoCould you be more specific why you say my load for VDD pin is not 300?Thanks.

author: Someone
author_rank: Super Contributor
timestamp: September 06, 2024, 09:15:13 pm
content: Quote from: john23 on September 06, 2024, 12:25:28 pmProof of a 300ohm load is on you, no-one else is claiming this. Imagine if the world had components which were non-linear... the horror!

author: john23
author_rank: Frequent Contributor
timestamp: September 07, 2024, 07:49:48 pm
content: Hello ,regarding the needs of the component:1.I can use a zener diode method to lower -12V into -2V as shown below.Is it a proper method for biasing the amplyfier?2.when we talk regarding the current needs then we need to put a load on that output.given the table fir the datasheet below Rload=V/I should I use R=0.8/15uA correct?3.How do i know what current needs to flow into the load?Thanks.https://www.minicircuits.com/pdfs/PMA5-83-2W+.pdf